Electrics
I.
II.
III.
IV.
V.
Direct current (DC)
Alternating current (AC)
Semiconductors
Basic knowledge of computers
Basic radio propagation theory
Direct current (DC):
A component consuming 80 watts at 8 amps would require a supply of:
A) 5 Volts
B) 0,01 kV
C) 100 Volts
D) 0.008 kV
In an aeroplane utilising a constant frequency AC power supply, DC power is obtained from a:
A) rotary converter.
B) static inverter.
C) 3 phase current transformer unit.
D) Transformer Rectifier Unit.
Aircraft standard fuses are fitted to:
A) AC circuits.
B) DC circuits only.
C) protect wiring in battery circuits only.
D) DC and AC circuits.
A 24V, 60 Ah battery is driving a 48 Watts light bulb. Approximately how long would the battery last
assuming that it is new?
A) 120 hours.
B) 30 hours.
C) 60 hours.
D) 2,5 hours.
Two resistors with values of 6 Ohm and 100 Ohm are connected in parallel. Their combined resistance is:
A) 5,66 Ohm.
B) 94 Ohm.
C) 106 Ohm.
D) 0,177 Ohm.
Magnetism can be used to generate electricity by converting mechanical energy to electrical energy
by:
A) electro
B) electro
C) electro
D) electro
magnetic conversion.
magnetic induction.
motive force.
self induction.
The operating principle of a fuse is:
A) a
B) a
C) a
D) a
wire with a predetermined melting point.
relay.
bimetallic strip.
high resistance metal wire.
Bonding is used to protect the aircraft against fire by:
A) providing an earth return system.
B) ensuring the same electrical potential of all metal components in the
aircraft's structure.
C) provision of an independent ignition system.
D) maintaining a different electrical potential throughout the aircraft's
structure.
If the power being drawn by a resistor is 100 watts from a 50V supply, what is the resistance of the
load?
A) 50 Ohms.
B) 25 Ohms.
C) 2 Ohms.
D) 4 Ohms.
The commutator of a DC generator converts:
A) DC to AC
B) AC to AC at a different voltage
C) AC to DC
D) DC to AC at a different voltage
In the following diagram A, B and C are
respectively the:
A) battery master switch, starter
relay, starter switch.
B) starter switch, battery master
switch, starter relay.
C) battery master switch, starter
switch, starter relay.
D) starter relay, starter switch,
battery master switch.
Recharging an aircraft's battery from an AC system would require:
A) a TRU.
B) an inverter.
C) nothing since the battery can supply AC as well.
D) a rectifier.
A rotary valve actuator is in the closed position. Its 'OPEN' limit switch is... and its 'CLOSE' limit switch
is...
A) open, closed
B) closed, open
C) open, open
D) closed, closed
When a battery is almost fully discharged there is a tendency for the:
A) electrolyte to " boil" .
B) current produced to increase due to the reduced voltage.
C) voltage to increase due to the current available.
D) voltage to decrease under load.
With regards to a light aircraft electrical system, where is the generator switch normally located?
A) In
B) In
C) In
D) In
series with the armature.
series with the cut-out switch.
series with the field winding.
parallel with the field winding.
The purpose of a battery protection unit is generally to isolate the battery:
1. from the bus when the battery charge is deemed satisfactory
2. when there is a battery overheat condition
3. in case of an internal short circuit
4. in case of a fault on the ground power unit
The combination which regroups all of the correct statements is :
A) 1, 2
B) 1, 2, 3, 4
C) 1, 2, 3
D) 1
In order that DC generators will achieve equal load sharing when operating in parallel, it is necessary
to ensure that:
A) their voltages are almost equal.
B) the synchronising bus-bar is disconnected from the busbar system.
C) equal loads are connected to each generator busbar before paralleling.
D) adequate voltage differences exists.
The power dissipated as heat by a resistance R with an applied voltage V carrying a current I can be
expressed as:
A) V x V / I.
B) I x I x R.
C) I x I / V.
D) I x R x R.
Aircraft systems are almost always:
A) earth return systems
B) earth return with static system emergency back up
C) single pole static systems
D) dipole systems
An aircraft has total services drawing 120 amps, essential services drawing 45 amps and vital services
drawing 5 amps. The designer has 50 Ah capacity batteries (at system voltage) available and wishes
to ensure that the aircraft can fly safely for at least 2 hours following a breakdown of electrical
generators. What configuration of batteries would be employed?
A) 3
B) 3
C) 6
D) 2
in
in
in
in
series.
parallel.
parallel.
parallel.
21. Impedance is:
A) the
B) the
C) the
D) the
combined
combined
combined
combined
effect
effect
effect
effect
of
of
of
of
resistance and reactance.
real and imaginary power.
resistance and conductivity.
power factor and phase angle.
Consider a battery voltage V, connected to R1 and R2 which are in parallel: If V is 250 volts, R1 is 500
Ohms but R2 is a very low resistance then:
A) The total current from the battery will approximate the current in R1.
B) R2 is insignificant.
C) A large total current will flow.
D) A small total current will flow.
A generator is taken Off-line by:
A) operating the field switch
B) manual operation of the generator cut-out
C) removing all loads
D) creating a short circuit.
Electrical batteries when connected in parallel provide... amp/hr capacity and... voltage.
A) increased; the same
B) reduced; increased
C) the same; increased
D) increased; reduced
The international symbol of electrical power is
A) U and it is measured in volts.
B) P and it is measured in watts.
C) R and it is measured in ohms.
D) I and it is measured in amperes.
The capacity of a battery is expressed in terms of:
A) internal resistance.
B) watts.
C) volts.
D) ampere-hours.
A 12 volt battery that has 1 dead cell:
A) has less capacity.
B) is unserviceable.
C) still has a voltage of 12V.
D) has its capacity reduced by 1/12th.
When an electrical circuit is open circuited:
A) resistance will be low
B) resistance will be zero
C) components will operate normally
D) resistance will be high
The unit of inductance is:
A) the
B) the
C) the
D) the
Farad.
Reactance.
Ohm.
Henry.
The inductance of several inductors connected in series can be calculated to be:
A) the
B) the
C) the
D) the
sum of the individual inductances divided by the number of inductors.
sum of the individual inductances.
inverse of the sum of the individual inductances.
inverse of the sum of the inverses of the individual inductances.
The purpose of the voltage regulator is to:
A) Keep
B) Keep
C) Keep
D) Keep
a
a
a
a
constant
constant
constant
constant
power output from the generator
frequency
voltage output from the generator
current output from the generator
What unit is used to measure potential difference between two points in an electrical circuit?
A) Ohm
B) Amps
C) Volts
D) Coulombs
True power is measured in:
A) Kilovolt-amperes.
B) Kilovolt-amperes-reactive.
C) Kilojoules.
D) Kilowatts.
When fully charged, what is the maximum voltage across a lead-acid cell?
A) 24 volts.
B) 2.2 volts.
C) 2 volts.
D) 12 volts.
In a supply system which is AC, DC requirements are provided by:
A) rotary inverter.
B) TRU's.
C) batteries.
D) a static inverter.
In normal conditions, generator output voltage is arranged to be:
A) as high as possible
B) exactly the same as battery voltage
C) less than battery voltage
D) higher then battery voltage
An ammeter indicates a high rate of charge after engine start. This...
A) is dangerous. The field circuit breaker should be tripped manually.
B) is dangerous. The engine should be shut down immediately.
C) indicates generator failure.
D) is only allowed for a short period.
Fuses are rated to a value by:
A) the number of amperes they will carry
B) their wattage
C) the number of volts they will pass
D) their resistance measured in ohms
The connection in series of two 12 volt / 40 amp hours batteries, will create a unit with the following
characteristics:
A) 24
B) 12
C) 24
D) 12
volt
volt
volt
volt
/
/
/
/
80
80
40
40
amp
amp
amp
amp
hours
hours
hours
hours
Usually, in conductive materials:
A) the resistance decreases with increasing temperature.
B) the resistance increases with increasing temperature.
C) resistance and temperature are not related.
D) the resistance remains constant regardless of temperature.
41. When carrying out battery condition check using the aeroplane’ s voltmeter:
A) no load should be applied to the battery because it would depress the
voltage.
B) the battery should be isolated.
C) the load condition is unimportant.
D) a load should be applied to the battery in order to give a better indication
of condition.
The total current flow in an electrical circuit with resistors in parallel is equal to...
A) the sum of all the currents in all the components divided by the number
of components.
B) the reciprocal of the sum of the current reciprocals.
C) the sum of all the current reciprocals.
D) the sum of all the currents in all the components in the circuit.
What are fuses rated in?
A) Watts.
B) Volts.
C) Ohm.
D) Amps.
Apparent Power is measured in:
A) KWR or WR.
B) KW or Watts.
C) KVA or VA.
D) KVAR of VAR.
An aircraft electrical circuit which uses the aircraft structure as a return path to earth, may be defined
as a
A) single pole circuit
B) semi-negative system
C) double pole circuit
D) complete negative system
Voltage is proportional to rate of change of current in a:
A) resistor.
B) inductor.
C) capacitor.
D) battery.
In a DC generator circuit the reverse current relay:
A) prevents the battery from too high a charging rate.
B) allows current to flow in both directions through the generator.
C) allows the charge rate to drop as the battery becomes charged.
D) prevents the battery from motoring the generator at low speeds and
when stationary.
Voltage is:
A) is also known as potential difference
B) an electro motive force
C) a measure of the electrical charge passing a point
D) a measure of the power gained
The difference in electrical potential in a circuit is measured in:
A) Amperes.
B) Volts.
C) Watts.
D) Joules.
When does a generator cut-out open?
A) When
B) When
C) When
D) When
generator voltage exceeds a certain value.
battery voltage exceeds generator voltage.
generator voltage exceeds battery voltage.
battery voltage exceeds a certain level.
On a self-exited DC generator, if the voltage regulator increases the current through the field windings
then:
A) The
B) The
C) The
D) The
intensity
intensity
intensity
intensity
of
of
of
of
the
the
the
the
field
field
field
field
decreases and the output voltage increases.
increases and the output voltage increases.
increases and the output voltage decreases.
decreases and the output voltage decreases.
The capacity of a typical lead acid battery for aviation use is
A) 4-8 Ah.
B) 24 V.
C) 12 Volts
D) 12-18 Ah.
The power in a direct current circuit is equal to:
A) R x I x V
B) V x I
C) V x R
D) I x R
The total current in a parallel circuit is equal to:
A) the sum of all the currents of all the components, divided by the number
of components
B) the sum of the current reciprocals
C) the reciprocal of the sum of the current reciprocals
D) the sum of all the currents of all the components in the circuit
Voltage is a measure of:
A) coulombs per joule.
B) potential differential.
C) current.
D) resistance to current.
The voltage regulator of a DC generator is connected in:
A) parallel with the armature and in parallel with the shunt field.
B) parallel with the armature and in series with the shunt field.
C) in series with the armature and in parallel with the shunt field.
D) series with the armature and in series with the shunt field.
A simple circuit has 4 amps flowing through a 5 ohm resistor. How much power is being used?
A) 20 watts.
B) 80 watts.
C) 100 watts.
D) 60 watts.
The connection in parallel of two 12 volt / 40 amp hours batteries, will create a unit with the following
characteristics:
A) 24
B) 24
C) 12
D) 12
volt
volt
volt
volt
/
/
/
/
40
80
80
40
amp
amp
amp
amp
hours
hours
hours
hours
The capacitance of several capacitors connected in series is equal to:
A) the sum of the individual capacitances.
B) the sum of the individual capacitances divided by the number of
capacitors.
C) the inverse of the sum of the individual capacitances.
D) the inverse of the sum of the inverses of the individual capacitances.
An Electromotive Force (EMF) can be measured with:
A) a Hall effect probe.
B) an ohmmeter.
C) an ammeter.
D) a voltmeter.
61. A spill of electrolyte from a NiCad battery onto someone's skin should be:
A) rinsed
B) rinsed
C) rinsed
D) rinsed
with
with
with
with
a weak alkali (e.g. potassium hydroxide)
a concentrated acid (e.g. sulphuric)
a weak acid (e.g. boric acid).
water and add sodium bicarbonate
Resistance is expressed in... and the basic SI units for it are...
A) Ohms, V/A
B) Ohms, R
C) Ohms, J/C
D) Farad, F
Voltmeters and ammeters usually indicate:
A) amplitudes.
B) mean values.
C) peak-to-peak values.
D) RMS values.
Current is expressed in... and the basic SI units for it are...
A) Coulombs, A/s
B) Amperes, C/s
C) Amperes, kg/s
D) Farad, A/s
Batteries are rated in:
A) Henry
B) Joule
C) Volts
D) Ampere hours and Volts
Which unit is commonly used for reactive power?
A) kWR.
B) kVAR.
C) kVA.
D) kW.
What is the purpose of a battery cut-out?
A) to connect the battery to the starter motor when starting the engine.
B) to open when the battery is fully charged.
C) to prevent the battery discharging to the bus-bar when the generator is
on-line.
D) to prevent the battery discharging into the generator.
The so called HOT BUSSES or DIRECT BUSSES are:
A) automatically connected to the battery if generators have failed
B) kept in operating conditions by an electrical resistance in the case of
energy failure
C) directly connected to the battery
D) providing an alternative current
On an aircraft with an earth return electrical system:
A) one lead of the battery and one lead of the electrical components are
connected to the aircraft structure
B) the static electricity is discharged through the tyres on landing
C) one lead of all electrical components is earthed and the other is
connected to the bonding system
D) the static electricity is discharged through a chain linkage dangled from
the ram air turbine under emergency conditions
The type of windings commonly used in DC starter motors are:
A) series wound.
B) series shunt wound.
C) shunt wound.
D) compound wound.
Consider a battery voltage V, connected to four resistors R1, R2, R3, R4. They are connected as two
pairs in parallel (R1 and R2, R3 and R4). The two pairs are connected in series: If R1 and R2 are both
8 Ohms, R3 is 6 Ohms, R4 is 3 Ohms, the total resistance of the circuit is:
A) 25 Ohms.
B) 6.16 Ohms.
C) 5.33 Ohms.
D) 6 Ohms.
Consider a battery voltage V, connected to three resistors R1, R2, R3. R2 and R3 are in parallel with
one another, and the combination of them is in series with R1. If R1 is 2 Ohms and has 6 volts across
it, R2 has 2 amps running through it and R3 is 6 Ohms, what is R2?
A) 3 Ohms.
B) Impossible to tell without also knowing total current from the battery.
C) Impossible to tell without knowing V.
D) 6 Ohms.
When refuelling an aircraft:
A) the bonding plug must be connected to the earth terminal.
B) the refuelling nozzle must be bonded to the fuel tank.
C) the continuity between nozzle and hose must be infinity.
D) there is no fire risk as both the bowser and aircraft are bonded by the
refuelling nozzle.
An aircraft has three batteries, each of 12 volts with a 40 Ah capacity, connected in series. The
resultant unit has:
A) a
B) a
C) a
D) a
voltage of 36 volts
voltage of 36 volts
voltage of 24 volts
capacity of 120 Ah
and
and
and
and
a
a
a
a
capacity of 120 Ah.
capacity of 40 Ah.
capacity of 80 Ah.
voltage of 12 volts.
The output voltage of DC generators used in aircraft is normally regulated by:
A) Controlling the current in the field windings
B) Controlling the current in the armature (anker) windings
C) Varying the RPM of the generator
D) Varying the torque applied to the generator
Which of the following statements best describes two resistors connected in parallel?
A) The combined resistance is always less than the smallest individual
resistance present.
B) Resistors should never be connected in parallel.
C) The combined resistance is always greater than the largest individual
resistance present.
D) The combined resistance is equal to the average of the individual
resistances.
What is the purpose of a voltmeter?
A) to measure voltage and is fitted in series with the component.
B) to measure potential difference and is fitted in series with the load.
C) to measure potential difference and is measured in parallel with the
component.
D) to measure current.
When being charged, the specific gravity of the electrolyte in a Ni-cad cell:
A) depends on the voltage applied.
B) increases.
C) exhibits little change.
D) decreases.
A current limiter fuse in a DC generation system is used to:
A) instantaneously rupture to limit the current in the load
B) limit the current in the field circuit
C) allow a short term overload before rupturing
D) limit the current in the armature
Voltage is proportional to charge on:
A) an inductance.
B) a battery.
C) a capacitor.
D) a resistor.
81. DC generators are rated in:
A) kVA.
B) kW.
C) kVAR.
D) kWA.
Obvious disadvantages using Lead-Acid batteries in airplanes are:
A) They are expensive compared to other batteries used in airplanes.
B) They only carry 12 volt, and most modern airplanes use 24 volt circuits.
C) They have insufficient capacity and is volume and weight inefficient.
D) The Lead-Acid battery is too heavy.
The purpose of protecting a circuit against excessive current conditions is:
A) to prevent battery run down when a generator has failed
B) to provide a means of controlling and distributing the current in a circuit
C) to prevent a reverse current causing failure of the equipment
D) to prevent deterioration and failure of the aircraft's wiring and switch gear by excess heat.
An aircraft has 3 navigation lights, each rated at 24 watts, which are connected in parallel and
supplied by a 12 volts battery. What would be the total current that the battery has to deliver to the
navigation lights circuit?
A) 1,5 Amperes.
B) 6 Amperes.
C) 2 Amperes.
D) 0,5 Amperes.
It may be determined that an aircraft is not properly bonded if:
A) static noises can be heard on the radio.
B) there is interference on the VOR receiver.
C) a circuit breaker pops out.
D) there is heavy corrosion on the fuselage skin mountings.
When two DC generators are operating in parallel, control of load sharing is achieved by:
A) an equalising circuit which, in conjunction with the voltage regulators,
varies the field excitation current of the generators.
B) an equalising circuit which, in turn, controls the speed of the generators.
C) carrying out systematic load-shedding procedures.
D) the synchronous bus-bar.
Consider a battery voltage V, connected to four resistors R1, R2, R3, R4. They are connected as two
pairs in parallel (R1 and R2, R3 and R4). The two pairs are connected in series: If R1 is twice R2, R3 is
half R4, and the current in R1 is 9 amps, the current in R4 is:
A) 3 amps.
B) 9 amps.
C) 18 amps
D) 4.5 amps.
Two 0.03 Henry inductors are placed in series. The resulting inductance is:
A) 0,09 H.
B) 0,06 H.
C) 0,015 H.
D) 0,03 H.
An aircraft has a battery with a capacity of 60 Ah. Assuming that it will provide its normal capacity and
is discharged in 10 hours:
A) it
B) it
C) it
D) it
will
will
will
will
deliver
deliver
deliver
deliver
60 amperes for 10 hours
6 amperes for 10 hours
4.8 amperes for 10 hours
60 amperes for 1 hour
What efficiency is required in order for a battery to pass a capacity test?
A) 90%
B) 60%
C) 50%
D) 80%
The purpose of bonding is:
A) to
B) to
C) to
D) to
protect against lightning strikes.
keep all parts of the aircraft at the same potential.
prevent static electrical charges building up.
keep the aircraft at zero potential.
Consider a battery voltage V and two resistors (R1 and R2) which are connected in series: If R1 is 2
ohms, R2 has 3 amps through it and 3 volts across it what is V?
A) At most, 3 volts.
B) 6 volts.
C) Impossible to tell without knowing R2.
D) 9 volts.
During normal cruise flight conditions a Ni-Cd battery's ammeter shows a high rate of charge. What
does this indicate?
A) it can be ignored as it is quite normal
B) that the generator should be disconnected from the bus bar
C) that a high demand is being made on the system
D) that a possible thermal runaway exists
When a centre zero ammeter is reading to the left:
A) the battery is discharging to the generator.
B) the battery is discharging to the system.
C) the generator is supporting the system.
D) no current is flowing.
A circuit breaker:
A) may be reset manually after the fault has been rectified.
B) can be reset on the ground only.
C) can only be reset after major maintenance.
D) is self resetting after the fault has been rectified.
The voltage of a fully charged lead-acid battery cell is:
A) 2,2
B) 1,8
C) 1,4
D) 1,2
V
V
V
V
A battery is made up of 5 NiCad cells, each having a voltage of 1.2V and a capacity of 20Ah,
connected in series. What is the resulting combination?
A) 30 V, 100Ah.
B) 12 V, 20Ah.
C) 6 V, 20Ah.
D) 6 V, 100Ah.
1 ampere equals:
A) 1,000 microamps
B) 1,000 milliamps
C) 1,000,000 millicoulombs per second
D) 1,000,000 milliamps
The advantages of grounding the negative pole of the aircraft structure are:
1. Weight saving
2. Easy fault detection
3. Increase of short-circuit risk
4. Reduction of short-circuit risk
5. Circuits are not single-wired lines
The combination regrouping all the correct statements is :
A) 1,
B) 1,
C) 1,
D) 2,
2,
3,
2,
3,
3
5
4
5
A 12 volt battery is connected to a 24 watt light bulb. The battery lasts for 10 hours. What is the
battery capacity?
A) 240 Wh.
B) 120 Vh.
C) 5 Ah.
D) 20 Ah.
101. 8 volts are applied to a 2 Ohm resistor. What current will flow?
A) 24 watts.
B) 4 coulombs.
C) 4 amps.
D) 6 coulombs per second.
In a multi engined aircraft, how are the ammeters usually arranged?
A) One
B) One
C) One
D) One
for
for
for
for
each load bus bar.
all generators.
each set of generators which are paralleled.
each generator.
If you double the EMF, you will:
A) halve current.
B) double power.
C) double resistance.
D) double current.
When a conductor cuts the flux of a magnetic field:
A) an electromotive force (EMF) is induced in the conductor
B) current will flow in accordance with Flemings left hand rule
C) there will be no effect on the conductor
D) the field will collapse
Electrical power is expressed in:
A) Coulombs
B) Amperes
C) Watts
D) Volts
A Ni-cad cell is fully charged. Its on load voltage is:
A) 2,2 volts.
B) 12 volts.
C) 24 volts.
D) 1,2 volts.
An earth return electrical system has:
A) two
B) one
C) two
D) two
leads from each service to the aircraft's structure
lead to the service and one lead to the structure
leads from the system to each service
leads from the system to the structure
The capacitance of several capacitors connected in parallel can be calculated to be:
A) the inverse of the sum of the individual capacitances.
B) the inverse of the sum of the inverses of the individual capacitances.
C) the sum of the individual capacitances.
D) the sum of the individual capacitances divided by the number of capacitors.
Parallel wound motors produce a... starting torque and their speed varies... with load.
A) high, moderately
B) high, slightly
C) low, significantly
D) moderate, only very slightly
The voltage regulator of a DC generator:
A) increases voltage when engine RPM increases
B) is used to limit generator voltage only when the engine is over speeding
C) ensures a reverse current flow when the electrical circuit is broken
D) maintains a constant voltage
R1 and R2 resistances are connected in parallel. The value of the equivalent resistance (Req) so
obtained is given by the following formula:
A) Req = R1 + R2
B) 1/Req = 1/(R1 + R2)
C) Req = R1 x R2
D) 1/Req = 1/R1 + 1/R2
In aeronautics, the most commonly used batteries are NiCad because...
A) their output voltage is more constant than lead-acid batteries
B) their electrolyte is neither corrosive nor dangerous
C) they weigh less than lead-acid batteries
D) they are cheaper than lead-acid batteries
The difference in electrical potential between two points in a circuit is measured in:
A) Amperes.
B) Coulombs.
C) Watts.
D) Volts.
Assume a constant speed DC generator providing a constant output voltage. If the electrical load
increases, the voltage regulator will:
A) increase the intensity of the excitation current.
B) maintain the intensity of the excitation current constant.
C) change the direction of the excitation current.
D) decrease the intensity of the excitation current.
The purpose of an inverter could be:
A) to supply DC power when the battery is out of service.
B) to convert AC into DC.
C) to provide emergency power to essential AC consumers from a battery
bus bar.
D) all answers are correct.
In a circuit containing reactive elements, the total current:
A) must be out of phase with the voltage.
B) may be out of phase with the voltage.
C) will be independent of voltage.
D) must be in phase with voltage.
An ammeter measures:
A) Amps per second.
B) power dissipated.
C) potential differences.
D) Coulombs per second.
A 12 volt battery has a rating of 24 Ah. If fully charged, how long can it supply current to a 12 volt, 24
watt bulb?
A) 48 hours.
B) 6 hours.
C) 12 hours.
D) 1 hour.
Which of the following is an appropriate substance to use to neutralise the electrolyte from a Nicad
cell?
A) A dilute solution of boric acid.
B) A concentrated solution of sodium bicarbonate.
C) Lead sulphate in powdered form.
D) A dilute solution of sodium bicarbonate.
If one of the 12 cells of a lead-acid battery is dead, the battery:
A) has 1/12 less voltage and less capacity, but can still be used.
B) has 1/12 less capacity, but can still be used.
C) is unserviceable.
D) has 1/12 less voltage, but can still be used.
121. What is load shedding?
A) a reduction of the voltage in the system
B) an increase in the current to services
C) reduction of the total loads
D) distributing of the load between generators
The voltage regulator of a DC generator is connected in:
A) parallel with the shunt field coil.
B) series with the shunt field coil.
C) parallel with the armature.
D) series with the armature.
A 12 volt lead acid battery has a broken connection in a cell, the battery:
A) will suffer from thermal runaway
B) provides 1/12th less voltage for the same time
C) is unserviceable
D) provides 1/12th less voltage for 1/12th less time
On board present aircraft, the batteries used are-mainly Nickel-Cadmium. Their advantages are:
1. low risk of thermal runaway
2. high internal resistance, hence higher power
3. good charging and discharging capability at high rating
4. wider permissible temperature range
5. good storage capability
6. sturdiness owing to its metal casing
7. the electrolyte density remains unchanged during charging
The combination of correct statements is:
A) 2,
B) 3,
C) 1,
D) 3,
3,
4,
2,
4,
4,
5,
5,
6,
5, 6
6
6, 7
7
When approaching discharge, the characteristics of a battery are as follows:
A) voltage
B) voltage
C) voltage
D) voltage
decreases,
decreases,
decreases,
decreases,
internal
internal
internal
internal
resistance
resistance
resistance
resistance
decreases
increases, especially with Ni-cads
unchanged
increases
The primary purpose of bonding the metallic parts of an aeroplane is to:
A) provide a single earth for electrical devices.
B) provide safe distribution of electrical charges and currents.
C) isolate all components electrically and thus make the static potential constant.
D) prevent electrolytic corrosion between mating surfaces of similar metals.
A bus-bar is:
A) a device permitting operation of two or more switches together.
B) a distribution point for electrical power.
C) a device which may only be used in DC circuits.
D) the stator of a moving coil instrument.
The detection of a feeder fault on a direct current circuit results in:
1. automatic disconnection of the generator from the aircraft AC busbar
2. opening of generator field current relay
3. opening of the main relay of the generator breaker
4. opening of balancing circuit connecting two generators
5. lighting of an indicator lamp
The combination of correct statements is:
A) 1,
B) 2,
C) 2,
D) 1,
2,
3,
4,
3,
3, 4, 5
4, 5
5
5
When being charged the specific gravity of the electrolyte in a lead-acid cell:
A) increases.
B) exhibits little change.
C) depends on current flow.
D) decreases.
A 3 microfarad capacitor is in parallel with a 6 microfarad capacitor. What is the combined
capacitance?
A) 9 microfarads
B) 2 microfarads
C) 3 microfarads
D) 4.5 microfarads
12.5 watts are being consumed by a 2 Ohm resistor. What voltage has been applied?
A) 6.25 volts.
B) Impossible to tell without knowing the current.
C) 5 volts.
D) 3.125 volts.
The on-load voltage of a lead-acid battery is... and is measured using...
A) 1.2 Volts, Voltmeter.
B) 2 Volts, Voltmeter.
C) 1.35 Volts, battery charger.
D) 2.2 Volts, Capacity meter.
A component that provides 115 VAC output after an input of 28 VDC is called:
A) A rotary transformer.
B) An inverter, static or rotary.
C) A transformer / rectifier unit.
D) A static rectifier.
A 2 Ohm resistor has 3 amps through it. What power is being consumed by the resistor?
A) 2 watts
B) 18 watts
C) 18 joules per second
D) 4.5 watts
Resistors in series act as..., resistors in parallel act as...
A) current subtractors, voltage dividers.
B) voltage dividers, voltage subtractors.
C) voltage dividers, current dividers.
D) current dividers, current subtractors.
Consider a battery voltage V, connected to three resistors R1, R2, R3. R2 and R3 are in parallel with
one another, and the combination of them is in series with R1. If R1 is 3 Ohms, R2 is 10 Ohms and R3
is 5 Ohms, what is the total resistance of the circuit?
A) 18 Ohms.
B) 1.58 Ohms.
C) 6.33 Ohms.
D) 7.31 Ohms.
In an electrical circuit with 28V, 7A and 4ohms, the dissipated power is equal to:
A) 28 Watts
B) 113 Watts
C) 196 Volts
D) 196 Watts
If the frequency of the supply in a series capacitive circuit is increased, the current flowing in the
circuit will:
A) decrease.
B) remain the same.
C) increase.
D) be zero.
Overloading an electrical circuit causes the fuse to blow. This:
A) fractures the fuse case.
B) disconnects the fuse from its holder.
C) melts the fuse link wire.
D) bends the bimetallic strip out of position.
One essential law of magnetism is:
A) Equal poles attracts each other and unequal poles repel each other.
B) Magnetic power equals the product of current and voltage.
C) A permanent magnet bar will always have a north and a south pole.
D) The distance between the poles does not affect the amount of attraction
between poles.
141. There is a maximum amount of flux which can be carried by a piece of ferromagnetic material.
This is due to:
A) energy loss due to hysteresis
B) saturation
C) residual magnetism
D) high coercivity
Electrical services are connected in parallel. When some are switched off:
A) current may increase or decrease, depending on battery internal
resistance
B) current increases
C) current decreases
D) current stays the same
Voltage is expressed in... and the basic SI units for it are...
A) Tension, C/J
B) Volteres, C/J
C) Emf, J/C
D) Volts, J/C
Switching a DC alternator off is achieved by:
A) Open circuiting the armature.
B) Open circuiting the field electromagnet.
C) Close circuiting the electromagnet.
D) Close circuiting the armature.
The SI unit used for measuring... is...
A) resistance, Ohms.
B) EMF, Amperes.
C) current, Volts.
D) energy, Watts.
What type of electrical circuit is usually protected using a current limiter?
A) High duty power distribution circuits
B) DC circuits only
C) Low duty power distribution circuits
D) Logic circuits
Consider a battery voltage V, connected to three resistors R1, R2, R3. R2 and R3 are in parallel with
one another, and the combination of them is in series with R1. If R2 is twice R3 and has 2 amps
running through it, the power consumed by R3 is 16 watts, V is 12 volts, what is the power consumed
by R1?
A) 24 watts.
B) 48 watts.
C) Impossible to tell without knowing either R1 or R2.
D) 72 watts.
What is the purpose of an ammeter?
A) to
B) to
C) to
D) to
measure
measure
measure
measure
emf when fitted in series with the component
current when fitted in series in the circuit
current when fitted in parallel in the circuit
resistance
If a DC circuit with a total resistance of 2 Ohms has 12 volts DC applied, then the resulting current is:
A) 10 A.
B) 24 A.
C) 6 A.
D) 0,167 A.
Consider a battery voltage V, connected to R1 and R2 which are in parallel: If V is 12 volts and R1 is 4
Ohms, what current is flowing through R2?
A) 3 amps.
B) Impossible to tell, but must be at most 3 amps.
C) Impossible to tell without further information.
D) Impossible to tell, but must be at least 3 amps.
Alternating current (AC):
When AC generators are operated in parallel, they must be of the same:
A) frequency and amperage.
B) voltage and frequency.
C) amperage and kVAR.
D) voltage and amperage.
The oil system of an IDG will be:
A) the same as the main hydraulic aircraft system.
B) drawn from a common reservoir shared by all engines and IDG's.
C) drawn from a common reservoir shared by all IDG's.
D) independent of all other IDG's and independent of the hydraulic system.
Typical aircraft AC system run on:
A) 50 Hz, 115 volts.
B) 400 Hz, 250 volts.
C) 50 Hz, 24 volts.
D) 400 Hz, 115 volts.
A unit that converts electrical DC into AC is:
A) an AC generator
B) an inverter
C) a thermistor
D) a transformer rectifier unit
When loaded, an induction motor:
A) can run at any speed, depending upon the applied load.
B) can run at any speed, depending on the applied voltage.
C) runs at exactly synchronous speed.
D) runs at less than synchronous speed.
Which of this circuit diagram symbols represents an
auto-transformer?
A) A.
B) C.
C) D.
D) B.
What is the purpose of a load sharing circuit?
A) To achieve identical voltage outputs on all generators
B) Control the alternators in parallel in order that each one takes a fair and equal share of the load
C) Shed all unnecessary loads automatically
D) To achieve the same output frequency before paralleling
The main purpose of a Constant Speed Drive unit is to:
A) take part in the voltage regulation.
B) take part in the balancing of reactive loads.
C) maintain a constant frequency.
D) mechanically protect the alternator drive shaft during coupling.
In a three phase star connected power system, to calculate phase voltage from line voltage:
A) Phase voltage is the same as line voltage in a three phase star connected power system.
B) Ufase = sqrt (3) x Uline in a three phase star connected power system.
C) The result depends on the phase angle difference.
D) Uline = sqrt (3) x Ufase in a three phase star connected power system.
A short circuit on a single pole electrical circuit could be caused by:
A) the
B) the
C) the
D) the
supply to a component being disconnected.
component earth connection earthed to the aircraft's structure.
component supply being in contact with the aircraft's structure.
battery negative lead becoming disconnected in flight.
A CSD unit which has been disconnected in flight:
A) may be reset on the ground only, after engine shut-down.
B) may be reset in flight using the reset mechanism.
C) automatically resets in flight providing engine rpm is below a given value.
D) automatically resets at engine shut-down.
If the supply frequency to an inductor is decreased, the reactance... and the current...
A) increases, decreases.
B) increases, increases.
C) decreases, decreases.
D) decreases, increases.
In a parallel AC supply system, the load is measured in:
A) kW
B) kW
C) kW
D) kW
/
/
/
/
kV.
kVAR.
kVA.
kW.
The output frequency of an AC generator depends on:
A)
B)
C)
D)
generator
generator
generator
generator
RPM..
RPM and number of phases.
RPM and number of pole pairs.
RPM, number of pole pairs and number of phases.
A rectifier is a unit that
A) prevents rectified current from occurring in the electrical system.
B) protects the electrical system from over voltages induced in the system
itself.
C) produces a DC output from AC input.
D) transforms one Ac-voltage to a greater / smaller AC-voltage.
The reason for using inverters in an electrical system is.
A) To
B) To
C) To
D) To
change
avoid a
change
change
the DC voltage.
short circuit.
DC into AC.
AC into DC.
If a circuit breaker trips, which of the following actions is acceptable?
A) Immediately reset it
B) Reset to a lower value only
C) Allow it to cool then make one attempt only to reset it
D) Under no circumstance attempt to replace it
On an earth return aircraft wiring circuit:
A) the negative pole is connected to the positive pole.
B) a second cable carries the return.
C) the negative pole is connected to the aircraft's structure.
D) the positive pole is connected to the aircraft's structure.
The purpose of static wick dischargers is to:
A) be able to fly higher because of less electrical friction.
B) dissipate static charge from the aircraft skin after landing.
C) provide a path to ground for static charges when refuelling.
D) dissipate static charge of the aircraft in-flight thus avoiding radio
interference as a result of static electricity.
In a frequency wild AC supply system, a constant frequency can be derived:
A) from
B) from
C) from
D) from
a TRU.
the APU.
an inverter.
frequency wild generator maintained at constant engine RPM.
21. When an underspeed fault is detected on an AC generator connected to the aircraft AC busbar, the
protection device opens:
A) generator breaker
B) exciter breaker and generator breaker
C) exciter breaker, generator breaker and tie breaker
D) exciter breaker
The output voltage of a transformer is twice as high as the input voltage. The transformation ratio is:
A) 50
B) 2
C) 1/2
D) depends on the number of turn of wire in the primary and secondary windings.
To convert from an RMS value to an amplitude it is necessary to:
A) multiply the RMS value by 1
B) multiply the amplitude by 2
C) divide the RMS value by 0,707
D) multiply the RMS value by 2
The speed of an asynchronous four-pole motor fed at a frequency of 400 Hertz is:
A) 800 revolutions per minute.
B) 12000 revolutions per minute.
C) 1600 revolutions per minute.
D) 6000 revolutions per minute.
A star connected three phase generator can be used for:
A) all multiphase equipment.
B) single phase equipment only.
C) single phase and/or three phase equipment.
D) three phase equipment only.
Reversing two phases of a three phase motor will:
A) cause the motor to stall and stop.
B) cause the motor to overheat and burn out.
C) cause the motor to reverse its direction of rotation.
D) have no effect on the motor.
The purpose of a CSDU is to:
A) maintain constant supply frequency.
B) ensure a constant mechanical load on the engine.
C) maintain a constant generator output voltage.
D) prevent the generator from overspeeding.
The rectification of a three phase supply can be effected by using a formation of... rectifiers in a bridge
circuit.
A) 2
B) 3
C) 6
D) 4
A 3 phase AC generator has 3 separate stator windings spaced at:
A) 90° .
B) 120° .
C) 45° .
D) 60° .
A carbon pile voltage regulator:
A) is not present on a shunt wound self excited DC generator.
B) is only used when paralleling generators.
C) compresses the carbon pile if the generator output voltage is too high.
D) reduces the compression of the carbon pile if the generator output
voltage is too high.
Generator paralleling through busbars is done to assure that:
A) the biggest generator gets the highest load.
B) all consumers receive the same generator voltage.
C) different consumers can be fed from different sources.
D) wiring is done properly, and so that we easily can detect errors in the system.
The most commonly used circuit protection device in modern aircraft is a
A) current limiter.
B) resistor.
C) fuse.
D) push and pull circuit breaker.
Electrical bonding of an aircraft is used to:
1. protect the aircraft against lightning effects.
2. reset the electrostatic potential of the aircraft to a value approximating 0 volt
3. reduce radio interference on radio communication systems
4. set the aircraft to a single potential
The combination regrouping all the correct statements is:
A) 3,
B) 1,
C) 1,
D) 2,
4
3, 4
2, 3
4
When loaded, a synchronous motor:
A) runs at exactly synchronous speed.
B) can run at any speed, depending on the applied voltage.
C) can run at any speed, depending upon the applied load.
D) runs at less than synchronous speed.
Static electricity in an aircraft is a fire hazard because:
A) sparks are produced which could ignite flammable materials.
B) aircraft tyres could become charged and burst.
C) excessive voltage on screening cables could cause arcing through insulation.
D) metal components overheat and could ignite flammable materials.
A brushless AC generator output is tapped:
A) From the rotor.
B) By a commutator instead.
C) By slip rings instead.
D) From the stator.
When a persistent over excitation fault is detected on only one AC generator, the protection device
opens the:
A) tie breaker.
B) exciter breaker, generator breaker and tie breaker.
C) exciter breaker and generator breaker.
D) generator breaker and tie breaker.
When AC generators are operated in parallel:
A) Reactive loads must be balanced.
B) Real loads must be balanced.
C) Neither need be balanced.
D) Both real and reactive loads must be balanced.
A star wound generator, can provide how many different voltage(s):
A) 3.
B) Unlimited.
C) 1.
D) 2.
The purpose of static wick dischargers is to:
A) eliminate radio interference.
B) reduce fire hazard during refuelling only.
C) prevent static charges from building up in flight only.
D) discharge static electricity on landing.
41. On starting, in a brushless AC generator with no commutator rings, the generator is activated by:
A) the main field winding.
B) the auxiliary winding.
C) a set of permanent magnets.
D) the stabilizer winding jointly with the voltage regulator.
In a solely inductive circuit, what is the relationship between current and voltage?
A) Current
B) Current
C) Current
D) Current
lags voltage and is proportional to frequency.
leads voltage and is proportional to frequency.
lags voltage and is inversely related to frequency.
leads voltage and is inversely related to frequency.
Can frequency wild AC generators be operated in parallel?
A) Always.
B) Only if the engines are running at the same speed.
C) In an emergency, to supply services for a limited time at risk of causing
further damage.
D) Never.
In flight, if the constant speed drive (CSD) temperature indicator is in the red arc the:
A) pilot must disconnect it and manually control the alternator.
B) pilot can disconnect it to allow it to cool and use it again.
C) pilot must disconnect it, and the generator is not available for the rest of
flight.
D) pilot has to throttle back.
A " trip-free" type circuit breaker is a circuit protection device which:
A) is free from the normal CB tripping characteristic
B) can be reset at any time
C) will not allow the contacts to be held closed while a current fault exists in
the circuit
D) will allow the contacts to be held closed in order to clear a fault in the
circuit
It may be determined that an aircraft is not properly bonded if:
A) there is interference on the VOR receiver.
B) static noises can be heard on the radio.
C) there is heavy corrosion on the fuselage skin mountings.
D) a circuit breaker pops out.
In which of the following circuits is a current limiter most likely to be fitted?
A) an EFIS display circuit
B) a low voltage DC circuit
C) a lighting circuit
D) a supply circuit
A carbon pile voltage regulator controls generator output using:
A) the
B) the
C) the
D) the
reverse current relay.
field coil.
armature feedback loop.
secondary coil.
A sine wave has a peak-to-peak voltage of 400 V. Its:
A) amplitude is 800 V.
B) frequency is 50 Hz.
C) RMS value is 284 volts.
D) RMS value is 141 V.
In a capacitive AC supply system, if frequency reduces:
A) inductive reactance increases.
B) current increases.
C) capacitive reactance reduces.
D) current reduces.
An auto-transformer:
A) converts AC to DC.
B) has a partially shared winding.
C) has an primary winding which is isolated from the secondary winding.
D) can be used for very large voltage step ups.
For high power applications, an AC motor driving a DC generator can be used as:
A) an auto-transformer.
B) an inverter.
C) a transformer.
D) a rectifier.
Circuit breakers protecting circuits may be:
A) reset at any time
B) used in AC and DC circuits
C) used only in DC circuits
D) used only in AC circuits
In order to produce an alternating voltage of 400 Hz, the number of pole pairs required in an AC
generator running at 6000 rpm is:
A) 8
B) 12
C) 24
D) 4
In what kind of an electrical machine might a squirrel cage be found?
A) Separately excited DC generator.
B) Synchronous Motor.
C) Induction Motor.
D) Self excited AC generator.
A constant speed drive unit mounted side by side with an AC generator is known as:
A) a synchronous unit.
B) an IDG.
C) an accessory gearbox.
D) a CSDU.
In a 3 phase delta connected AC generator:
A) line
B) line
C) line
D) line
current is less than phase current.
current is equal to phase current.
voltage is equal to phase voltage.
voltage is greater than phase voltage.
In a generator, the Constant Speed Drive (CSD):
1. may be disconnected from the engine shaft
2. may be disconnected from the generator
3. is a hydro-mechanical system
4. is an electronic system
5. may not be disconnected in flight
6. may be disconnected in flight
A) 1,
B) 2,
C) 1,
D) 1,
2,
3,
3,
4,
5
4
6
5
Which of the following is a symptom of an open circuit on one phase in a three phase generator?
A) Two phases failed only.
B) Thermal damage to the stator.
C) An increase in neutral current.
D) One line failed only.
In the event of mechanical failure in the generator, the CSDU is protected by:
A) an automatic clutch.
B) a quill drive.
C) a manually operated dog-tooth clutch.
D) movement of the swash plate in the CSDU pump to minimise output.
61. In an inductive circuit, current:
A) lags voltage by 90° .
B) is in phase with voltage.
C) leads voltage by 90° .
D) leads voltage by 180° .
Static dischargers:
1. are used to set all the parts of the airframe to the same electrical potential
2. are placed on wing and tail tips to facilitate electrical discharge
3. are used to reset the electrostatic potential of the aircraft to a value approximating 0 volts
4. are located on wing and tail tips to reduce interference with the on-board radio communication
systems to a minimum
5. limit the risks of transfer of electrical charges between the aircraft and the electrified clouds
The combination regrouping all the correct statements is:
A) 3,4,5
B) 2,4,5
C) 1,2,5
D) 1,3,4
Bonding is a method of:
A) ensuring that the different parts of the aircraft are maintained at the
same potential.
B) ensuring that the different parts of the aircraft are maintained at a
different potential.
C) providing an earth return.
D) ensuring structural integrity.
The aviation industry standard that has evolved for constant frequency aircraft is 115/200V AC, 3
phase, 400 Hz. The 115/200V are:
A) peak-to-peak values.
B) DC values.
C) amplitude values.
D) RMS values.
The efficiency of modern transformers is:
A) between 30% and 75%.
B) less than 30%.
C) between 75% and 90%.
D) more than 90%.
If it is necessary to disconnect a CSDU from an engine how is this achieved?
A) A
B) A
C) A
D) A
hydraulic clutch.
quill drive.
generator tie breaker.
dog clutch.
The frequency of the current provided by an alternator depends on...
A) its phase balance
B) the strength of the excitation current
C) its load
D) its rotation speed
In a carbon pile voltage regulator, when the pile is compressed its resistance... and the current
through the field coil:
A) decreases, decreases
B) increases, decreases
C) decreases, increases
D) increases, increases
Oil for a CSDU is supplied by:
A) the oil system common to all engines.
B) the associated engine oil system.
C) the oil system common to all CSDU's.
D) its own independent oil supply.
In an alternator rotor coil you can find:
A) Three-phase AC
B) AC
C) Only induced current
D) DC
A generator has a 4 pole pair field electromagnet on its rotor. It has 3 phase output windings on its
stator. If the rotor RPM is 300, what is the output frequency?
A) 20 Hz.
B) 15 Hz.
C) 900 Hz.
D) 1200 Hz.
The purpose of a CSDU is to:
A) rotate the stator at a constant RPM.
B) rotate the field electromagnet at a constant RPM.
C) maintain a constant RPM of the carbon brushes.
D) rotate the accessories gearbox at a constant RPM.
An aircraft without constant speed generator drive systems or VSCF's will have a...
A) random frequency supply.
B) frequency oscillating supply.
C) frequency wild supply.
D) variable amplitude supply.
A transformer has 150 turns on the primary winding with 240 volts applied. The secondary winding
has 25 turns.
If a 10 ohm resistive load is present across the secondary it will have a voltage across it of:
A) 40 V.
B) 115 V.
C) 1200 V.
D) 150 V.
High circulating currents on the real load of paralleled AC generators is the result of:
A) an
B) an
C) an
D) an
out of balance reactive load control coil.
imbalance of frequency between generators.
imbalance of field current on the reactive load.
imbalance of voltage outputs.
A magnetic circuit breaker:
A) is a quick tripping response protective system
B) has a slow response time
C) permits over voltage for a short period of time
D) can be reset without danger
A reverse current cut-out operates based on the difference between:
A) reverse current and forward current.
B) generator current and battery current.
C) the difference in generator voltages on a multi-engine aircraft.
D) bus bar voltage and generator voltage.
The purpose of a voltage regulator is to control the output voltage of the:
A) generator at varying loads and speeds.
B) generators at varying speeds and the batteries at varying loads.
C) output of the TRU.
D) batteries at varying loads.
On the flight deck, an oil operated CSD unit is normally provided with means of monitoring the:
A) oil temperature and synchronous speed.
B) output speed and oil pressure.
C) oil over-temperature and low oil pressure.
D) low oil temperature and low oil quantity.
How is a low reactive load on one AC generator, of paralleled AC generators, compensated for?
A) reducing the overall load.
B) increasing the real load on the other generators.
C) altering the excitation current in its field circuit.
D) increasing generator RPM.
81. A squirrel cage would be found in:
A) a synchronous motor.
B) a CSDU.
C) an IDG.
D) an induction motor.
A thermal circuit breaker:
A) forbids any overcurrent.
B) is a protection system with a quick break capacity of about one
hundredth of a second.
C) can be reset without any danger even if the fault remains.
D) protects the system in the event of overheating, even without exceeding
the maximum permissible current.
The most common voltage / frequency used in jet transport A/C is:
A) 400 VAC / 115 Hz
B) 115 VAC / 400 Hz
C) 28 VDC
D) 115 VDC / 400 Hz
A BTB is:
A) a break tie bus.
B) bus tension bar.
C) a bus-to-bus relay.
D) a bus tie breaker.
During normal operation of a split bus bar AC supply system, the batteries are connected to:
A) the
B) the
C) the
D) the
vital bus bar
vital bus bar
essential DC
essential DC
and are charged by the TRU's.
and are charged by the generators.
bus bar and are charged by the alternators.
bus bar and are charged by the TRU's.
The CSDU... should be operated with the engine...
A) disconnect, running at greater than idle RPM.
B) quill drive, running at idle RPM.
C) quill drive, running at greater than idle RPM.
D) disconnect, at idle RPM.
If the oil temperature gauge of the CSD is in the red what would action is required?
A) Auto disconnect
B) Throttle back and allow to cool down
C) Disconnect, then when cooled reconnect
D) Manually disconnect and reconnect on the ground
A transformer has 500 turns of wire on the primary winding and 50 turns of wire on the secondary
winding. If 240 Volts AC is applied across the primary, the output voltage across the secondary coil
will be:
A) 2,4 kV.
B) 218 Volts.
C) 0 Volts as transformers can only change the mean value of the voltage.
D) 24 Volts.
The purpose of a TRU is to convert:
A) AC to DC.
B) AC to DC and change the voltage.
C) DC to AC.
D) DC to AC and change the voltage.
A single phase AC stator with a shaded pole can be used to:
A) Drive an induction motor designed for starting under heavy load.
B) Create a field with a weak rotating element.
C) Create a unidirectional field only.
D) Created a field with a fixed orientation.
A multi engine aircraft with one generator per engine has:
A) one
B) one
C) one
D) one
ammeter per battery.
ammeter per generator.
ammeter.
ammeter, connected in series, to show total output.
What is the shaft RPM of a synchronous AC motor connected to a 3 phase 200 Hz supply?
A) 600 rpm
B) 200 rpm
C) 3.3 rpm
D) 12,000 rpm
In an aeroplane equipped with a DC main power system, AC for instrument operation may be obtained
from:
A) a rectifier.
B) an inverter.
C) a contactor.
D) a TRU.
When selecting a fuse for an aircraft circuit the governing factor is:
A) the
B) the
C) the
D) the
voltage of the circuit.
resistance of the circuit.
power requirement of the circuit.
energy of the circuit.
Which unit is commonly used for reactive power?
A) kWR.
B) kW.
C) kVA.
D) kVAR.
What happens to the current in a series capacitive circuit when frequency increases?
A) Increases or decreases depending on the capacity of the circuit.
B) Current increases.
C) Current decreases.
D) Current neither increases nor decreases.
Generators are usually:
A) excited by a permanent magnet.
B) self excited.
C) externally excited.
D) unexcited.
The moving part of an AC generator is:
A) the
B) the
C) the
D) the
rotor.
phase winding.
stator.
squirrel cage.
When paralleling alternators, reactive loads are controlled by:
A) generator speed.
B) voltage.
C) frequency.
D) torque.
A transformer converts:
A) the value of alternating voltage.
B) low frequency signals to high frequency signals.
C) the mean value of alternating voltage.
D) AC signals to DC.
101. When illuminated, what is indicated by the warning lights of an AC generators constant speed
drive?
A) Excessive voltage and current.
B) Excessive temperature and low RPM.
C) High temperature and high oil pressure.
D) Excessive temperature and low oil pressure.
A Constant Speed Drive aims at ensuring
A) that the CSD remains at a constant RPM not withstanding the generator
RPM
B) that the electric generator produces a constant frequency.
C) equal AC voltage from all generators.
D) that the starter-motor maintains a constant RPM not withstanding the
acceleration of the engine.
Real load sharing in a parallel AC system is achieved by:
A) monitoring the kVAR of each generator/alternator.
B) carefully selecting the number of loads on the bus-bars at any one time.
C) controlling the generator field current.
D) adjusting the torque on each generator rotor via the CSD unit.
In a perfect capacitor, as frequency increases, impedance:
A) decreases.
B) depends on resistance.
C) increases.
D) stays the same.
What is the purpose of a commutator on an AC generator?
A) To convert DC power into AC power.
B) To convert AC power into DC power.
C) To decrease the electrical noise caused by sparking.
D) An AC generator has no commutator.
In an AC circuit as a whole, current equals:
A) resistance/voltage.
B) voltage/resistance.
C) voltage/reactance.
D) voltage/impedance.
Assuming a CSD fault is indicated, the CSD should be disconnected:
A) at flight idle engine rpm.
B) on the ground only.
C) in accordance with the regulated voltage level of the AC generator.
D) during engine operation only.
The most widely used AC frequency in aircraft is:
A) 50 Hz
B) 400 Hz
C) 60 Hz
D) 100 Hz
If two constant frequency AC generators are operating independently, then the phase relationship of
each generator:
A) must be 240° out of phase.
B) must be synchronised.
C) is unimportant.
D) must be 120° out of phase.
Power factor is defined as:
A) the
B) the
C) the
D) the
ratio
ratio
ratio
ratio
of
of
of
of
real current to apparent current.
apparent current to imaginary current.
imaginary current to real current.
real current to imaginary current.
The output frequency of a 3 phase AC generator with a shaft RPM of 8,000 is:
A) 24 kHz.
B) 44 Hz.
C) 133 Hz.
D) 400 Hz.
The function of a CSD in an AC generating system is to:
A) vary the engine rpm (within limits) to compensate for various AC loads.
B) vary generator rpm in order to compensate for various AC loads.
C) directly maintain a constant proportion between the rpm of engine and generator.
D) drive the generator at a constant speed.
The function of the Generator Breaker is to close when the voltage of the:
A) battery is greater than the generator voltage and to open when
opposite is true
B) generator is greater than battery voltage and to open when the
is true
C) battery is greater than the alternator voltage and to open when
opposite is true
D) alternator is greater than the battery voltage and to open when
opposite is true
the
opposite
the
the
Two AC signals that have equal amplitude and frequency may not be at the same point in their cycles
at any given moment. This is known as:
A) being in phase.
B) phase overlap.
C) being unsynchronised.
D) being out of phase.
As regards the Generator Control Unit (GCU) of an AC generator, it can be said that:
1. The GCU controls the AC generator voltage
2. Modern GCUs are provided with a permanent indication to record the failure
3. All the commands originating from the control panel are applied via the GCU, except dog
clutch release
4. The Auxiliary Power Unit (APU) provides the excitation of the AC generator as soon as the APU
starts up
The combination regrouping all the correct statements is:
A) 1,
B) 2,
C) 2,
D) 3,
3
3
4
4
A rectifier converts:
A) a three phase input into a single phase output.
B) a single phase input into a three phase output.
C) AC to DC.
D) DC to AC.
To ensure correct load sharing between AC generators operating in parallel:
A) only real loads need to be matched.
B) only reactive loads need to be matched.
C) the matching of loads is unimportant.
D) both real and reactive loads must be matched.
Paralleled AC alternators, when fitted to an aircraft supply system will have:
A) one
B) one
C) one
D) one
loadmeter which measures total system load only.
load meter for each generator.
meter which indicates both frequency and voltage.
voltmeter for each generator.
In a star connection, line voltage equals... and line current is equal to...
A) 1.73 x phase voltage; phase current.
B) 3 x phase voltage; 1.73 x phase current.
C) phase voltage; phase current.
D) phase voltage; 3 x phase current.
In a generator circuit, the circulating current is:
A) the current needed to excite the generator.
B) the current flowing between two unbalanced generators.
C) rotating in the stator assembly.
D) the total load on the generator armature.
121. A generator is 'on line':
A) when
B) when
C) when
D) when
operational excitation is achieved.
idle rpm is achieved at engine starting.
the generator is connected to the bus bar.
the generator reaches its operational rpm.
What influences the speed of rotation of a synchronous motor?
A) Current.
B) Supply frequency.
C) Voltage.
D) Reactance.
Load shedding means:
A) Temporary or permanent switching off of certain electric users to avoid
overload of electric generators
B) A procedure used in control systems to reduce the stick forces
C) To leave behind extra cargo if the centre of gravity moves outside limits
D) Reduction of airloads on the flaps by means of the flap load relief valve
A fuse which is used to protect an electrical circuit:
A) has
B) has
C) has
D) has
a
a
a
a
high internal resistance.
high melting point.
low flash point.
low melting point.
Which of this circuit diagram symbols represents a relay?
A) B.
B) A.
C) D.
D) C.
For a star connected AC generator, which of the following statements is true?
A) The neutral point is used as the earth return in modern aircraft.
B) All these statements are true.
C) Line current = phase current.
D) Line voltage = 1,73 x phase voltage.
The purpose of a split field motor is to allow it to be run:
A) at two different speeds
B) at two different system voltages
C) in two different directions
D) on either a negative or a positive earth system
Real load sharing is achieved by:
A) Paralleling frequency wild supplies.
B) Frequency control.
C) Voltage regulation.
D) Reactive sharing.
Ferromagnetic materials are good at carrying magnetic flux because they have a:
A) low reluctance.
B) high resistance.
C) low resistance.
D) high reluctance.
Which of the following statements regarding external power is true for most airliners?
A) External power can not be paralleled with any of the aircraft generators
B) External power can usually be paralleled with the APU generator, but not
with the main generators
C) External power can usually be paralleled with the main generators, but
not with the APU generator
D) External power can be paralleled with all aircraft generators
When a persistent top excitation limit fault on an AC generator connected to the mains with another
AC generator, the over excitation protection device opens:
A) the
B) the
C) the
D) the
tie breaker.
exciter breaker and the generator breaker.
exciter breaker, the generator breaker and the tie breaker.
generator breaker.
An example of a motor providing a weak rotating field by a single phase AC supply is:
A) a uni-directional motor.
B) None of the above.
C) a uni-synchronous motor.
D) an induction motor with a split phase winding.
kVAR is a unit which is used for:
A) reactive (or imaginary) power.
B) apparent power.
C) real power.
D) total power.
The most common three phase alternator connection is:
A) a
B) a
C) a
D) a
self excited connection.
separately excited connection.
star connection.
delta connection.
To operate in parallel without damage occurring, generators must have:
A) same number of phases.
B) same frequency and same phase sequence.
C) all statements are true.
D) equal voltage and power ratings.
On detection of a persistent overvoltage/fault on an AC generator connected to the aircraft AC
busbars, the on- board protection device opens:
A) the
B) the
C) the
D) the
exciter breaker, the generator breaker and tie breaker
generator breaker and tie breaker
generator breaker
exciter breaker and the generator breaker
The voltage output of a shunt wound generator:
A) will rise gradually as load is applied.
B) will fall gradually as load is applied.
C) will depend on the inductance on the field coil in series with the
armature.
D) will remain constant as the electrical load increases.
Real load sharing in an AC power system is achieved by:
A) voltage control via the field windings.
B) torque control via the CSDU.
C) frequency control via the field windings.
D) voltage control via the CSDU.
Most practical alternators are designed with a...
A) rotating field and a stationary armature.
B) stationary field and stationary armature.
C) rotating field and rotating armature.
D) rotating armature and a stationary field.
The most widely used electrical frequency in aircraft is:
A) 200 Hz.
B) 50 Hz.
C) 400 Hz.
D) 60 Hz.
141. An inverter converts:
A) AC into DC.
B) DC into AC.
C) a single phase input into a three phase output.
D) a three phase input into a single phase output.
The main difference between a fuse and a circuit breaker is that:
A) The fuse can be reset after having been tripped, the circuit breaker can not.
B) The fuse has to be replaced, but the circuit breaker can be reset.
C) The circuit breaker is used for high loads, while the fuse is used for small,
electronic loads.
D) The circuit breaker is used to protect inductive loads, while the fuse is
used to protect resistive loads, otherwise no difference.
An AC generator driven by a CSD unit:
A) requires a voltage controller to maintain constant frequency.
B) does not need a voltage controller since an AC generator voltage cannot
alter under load.
C) requires a voltage controller to maintain constant voltage under load.
D) does not need a voltage controller since the CSD will ensure constant voltage.
How are fuses rated?
A) In
B) In
C) In
D) In
amperes
Ampere-hours
Ohms depending on the impedance
volts
A star wound generator, with a TRU attached, could be designed to provide... different voltage(s) from
a given AC supply.
A) 3
B) unlimited
C) 6
D) 1
A compound wound generator is one in which:
A) the
B) the
C) the
D) the
voltage rises with increase in load
voltage falls when the load increases
field is separately excited
voltage remains constant with increase in load
Synchronising bus bars are used:
A) to supply essential services.
B) to share real load between the alternators in a split bus system.
C) to supply non-essential services in case of accidental loss of all
generators.
D) to connect two or more alternators in parallel.
The output of an AC generator is rated in:
A) kW.
B) kW / kVAR.
C) kVA.
D) kW / kW.
Semiconductors:
A diode is:
A) all statements are true
B) a semiconductor formed from N-P type material
C) a semiconductor formed from P-N type material
D) a rectifier
A transistor is a:
A) PN junction
B) NP junction
C) PNP or NPN junction
D) PNP junction
Which component is presented in the following diagram?
A) A PN transistor
B) A PNP transistor
C) An NP transistor
D) An NPN transistor
This symbol represents:
A) a diode
B) a transistor
C) an XNOR gate
D) a thyristor
What type of transistor is represented by the following symbol. What are
the terminals A,B and C?
A) An NPN transistor with base, collector and
Emitter
B) A PNP transistor with base, emitter and collector.
C) A PNP transistor with base, collector and emitter
D) An NPN transistor with base, emitter and
collector
A transistor has... current paths which are...
A) three; positive emitter path, base emitter path and collector emitter path
B) two; base emitter path and collector emitter path
C) two; positive emitter path and base emitter path
D) three; positive-negative-positive
Which of the following materials are used for the manufacturing of semiconductors?
A) silver, germanium and silicon
B) polythene, silicon and steel
C) silicon, cadmium and germanium
D) copper, silver and germanium
A relay is:
A) a magnetically operated switch.
B) a device which is used to increase electrical power.
C) a unit which is used to convert electrical energy into heat energy.
D) another name for a solenoid valve.
A diode:
A) allows current to flow in one direction only
B) allows current flow if it is in phase with the voltage
C) can be used as an inverter
D) allows current flow if its lags the voltage by 90 degrees
A relay is:
A) an electrical security switch.
B) an electrical energy conversion unit.
C) an electromagnetically operated switch.
D) a switch specially designed for AC circuits.
What are terminals A,B and C in the following diagram.
A) Anode, cathode and collector
B) Collector, anode and cathode
C) Base, emitter and collector
D) Base, collector and emitter
Semiconductors are manufactured from:
A) duralumin
B) germanium
C) plastic
D) hiduminium
A junction diode:
A) is a
B) has
C) has
D) is a
PNP junction
low resistance in both directions
high resistance in one direction
PNP or a NPN junction
The letters PNP when related to a transistor denote:
A) positive, negative, positive
B) polar, normal, positive
C) positive, negated, positive
D) positive, neutral, positive
How many diodes are required in a three phase full wave bridge rectifier?
A) 4
B) 6
C) 3
D) 1
A transistor has:
A) two terminals
B) a single terminal
C) no terminals
D) three terminals
Basic knowledge of computers:
The logic symbol shown represents (assuming
positive logic):
A) a NOR gate
B) an EXCLUSIVE gate
C) a NAND gate
D) an INVERT or NOT gate
An AND gate is sometimes referred to as:
A) a - something or nothing - gate.
B) an - all or nothing - gate.
C) an - anything goes - gate.
D) an - any or all - gate.
In electronic terms, what is a flip-flop?
A) a
B) a
C) a
D) a
paralleled capacitor.
memory multivibrator.
bistable multivibrator.
shift register.
What does the following symbol in an electronic circuit represent?:
A) A NOR gate
B) A NAND gate
C) An AND gate
D) An OR gate
What logic function is achieved by the following circuit,
where A and B are the inputs and C is the output?
A) XNOR
B) NAND
C) AND
D) NOR
For this diagram, choose the answer which
correctly states the outputs from the logic
circuit shown:
A) Both C and D are equal to 0.
B) C=1 and D=0.
C) C=0 and D=1.
D) Both C and D are equal to 1.
What does the following symbol represent?
A) An invert gate
B) A flip-flop
C) A toggle switch
D) A diode
What is the proper name for an " all or nothing" gate?
A) XOR
B) NOT
C) OR
D) AND
What does the following truth table represent?
A) OR.
B) Exclusive AND.
C) Exclusive OR.
D) NOR.
Inputs and outputs of logic gates are generally:
A) of
B) of
C) of
D) of
a zero current nature
high current
low current and termed signals
low voltage and termed pulsated signals
In computer technology, an EPROM is:
1. a read-only memory
2. a write memory
3. erases its content when power supply is cut off
4. keeps its content when power supply is cut off
The combination regrouping all the correct statements is:
A) 1,4
B) 2,3
C) 1,3
D) 2,4
The following symbol represents an... logic gate.
A) AND.
B) NAND.
C) XOR.
D) NOT.
For this diagram, choose the answer which
correctly states the outputs from the logic
circuit shown:
A) C=1 and D=0.
B) C=0 and D=1.
C) Both C and D are equal to 0.
D) Both C and D are equal to 1.
Which of the following are logic gates?
A) XOR and NAND.
B) Exclusive and NOT exclusive.
C) Exclusive and OR.
D) XOR and VOR.
What does the following truth table represent?
A) A NAND gate.
B) A NOR gate.
C) An OR gate.
D) An XOR gate.
The symbol on the picture represents:
A) an EXCLUSIVE OR gate
B) an OR gate
C) an AND gate
D) a NOT gate
This symbol is:
A) a NOR gate.
B) a NAND gate.
C) an AND gate.
D) an OR gate.
What is the name of the following logic gate?
A) NOT.
B) AND.
C) XOR.
D) OR.
If all the inputs and outputs to and from an OR gate are inverted, the equivalent logic function is:
A) EXNOR
B) OR
C) AND
D) NOR
Which logic gate is the equivalent of the circuit below with inputs A
and B and output C?
A) XOR
B) AND
C) OR
D) NOT
21. Because of the input/output relationship of an AND gate, it is often referred to as the:
A) "
B) "
C) "
D) "
inhibited" or " negated" gate.
all or nothing" gate.
any or all" gate.
state indicator" gate.
Which gate has the following truth table?
A) XOR
B) NOT
C) AND
D) OR
In which of the following logic gates are contained the six most common gates?
A) AND, NOR, NAND
B) NAND, NOR, EXOR
C) NAND, INHIBITED AND, and OR
D) OR, NAND and NOT
For this diagram, choose the answer which
correctly states the outputs from the logic
circuit shown:
A) Both C and D are equal to 0.
B) C=1 and D=0.
C) Both C and D are equal to 1.
D) C=0 and D=1.
The logic symbol shown represents an...
gate.
A) NAND
B) NAND
C) XOR
D) NOT
An OR gate is sometimes referred to as:
A) something or nothing - gate.
B) all or nothing - gate.
C) any or all - gate.
D) anything goes - gate.
An EXCLUSIVE OR gate with only two inputs, which gives a high output when either input is 1, will:
A) give an output 0 when both inputs are high.
B) only give a high output when both inputs are at logic state 0.
C) give an output 0 when only one input is at logic state 1.
D) also give a high output when both inputs are logic state 1.
The following symbol represents ... logic
gate.
A) NAND
B) XOR
C) NOT
D) AND
A logic gates function is to:
A) increase output power.
B) close a set of switches in a logical sequence.
C) match the input to the output.
D) send an appropriate output depending on the input.
The smoke detection in the aircraft cargo
compartments is carried out by four sensors: C1, C2,
C3 and C4. They are associated with the logic circuit
as described by the diagram. The repeating bell is
activated when:
A) the C1 and C3 sensors detect smoke
B) the C1 and C2 sensors detect smoke
C) only one sensor detects smoke
D) the C2 and C4 sensors detect smoke
In computer technology, an output peripheral is a:
A) hard disk drive
B) screen unit
C) diskette drive
D) keyboard
For this diagram, choose the answer which correctly
states the outputs from the logic circuit shown:
A) C=1 and D=0.
B) Both C and D are equal to 1.
C) C=0 and D=1.
D) Both C and D are equal to zero.
The following symbol represents an... logic
gate.
A) XNOR
B) OR
C) NOT
D) AND
The following symbol represents an... logic
gate.
A) NOT
B) OR
C) XNOR
D) AND
What is an any or all gate?
A) XOR
B) NOT
C) NOR
D) OR
In computer technology, a storage peripheral is a:
A) screen unit
B) printer
C) key board
D) hard disk drive
The following symbol represents an... logic
gate.
A) AND
B) XNOR
C) NOR
D) NOT
Because of the input/output relationship of an OR gate, it is often referred to as the:
A) "
B) "
C) "
D) "
state indicator" gate.
any or all" gate.
inhibited" or " negated" gate.
all or nothing" gate.
If a logic gate is referred to as an 'All Or Nothing' gate it is:
A) an
B) an
C) an
D) an
AND-gate.
XNOR-gate.
OR-gate.
XOR-gate.
In computer technology, an input peripheral is a:
A) screen unit
B) diskette drive
C) hard disk drive
D) keyboard
41. The function of a NOT logic gate within a circuit is to:
A) invert the input signal such that the output is always of the opposite state.
B) ensure the input signal is DC only.
C) ensure the input signal is AC only.
D) ensure the output signal is of the same state as the input signal.
A bar above a logic gate input letter indicates:
A) a negated input.
B) an inhibited input.
C) a prohibited input.
D) an inverted input.
Which logic gate is equivalent to the following combination:
A) NAND
B) XOR
C) OR
D) NOR
For this diagram, choose the answer
which correctly states the outputs from
the logic circuit shown:
A) Both C and D are equal to 1.
B) C=1 and D=0.
C) Both C and D are equal to 0.
D) C=0 and D=1.
Basic radio propagation theory:
The VHF direction finder uses the following wavelengths:
A) hectometric.
B) decimetric.
C) metric.
D) centimetric.
If the strength of a radio signal decreases away from the transmitter, this effect is called:
A) attenuation.
B) refraction.
C) ducting.
D) amplification.
In aviation, the reflection on ionosphere layers phenomenon is used in the following frequencies:
A) UHF
B) HF
C) VHF
D) VLF
A radio signal has a frequency of 225MHz and is transmitted through a typical di-pole aerial. For it to
work efficiently what is the required length of the aerial?
A) 13 cm.
B) 2/3 m.
C) 1,3 m.
D) 0,07 m.
The Distance Measuring Equipment (DME) uses the following wavelengths:
A) metric.
B) hectometric.
C) centimetric.
D) decimetric.
The Instrument Landing System (ILS) uses the following wavelengths:
A) metric.
B) centimetric.
C) hectometric.
D) decimetric.
Which statement is true?
A) The attenuation of an HF ground wave is worse over the land than over
ice.
B) None of the above.
C) The lower the frequency the greater the atmospheric attenuation.
D) The ionosphere will attenuate and refract signals up to 30 GHz.
The skip zone of HF-transmission will increase when the following change in circumstance occurs:
A) Higher frequency and lower position of the reflecting ionosphere layer
B) Lower frequency and lower position of the reflecting ionosphere layer
C) Lower frequency and higher position of the reflecting ionosphere layer
D) Higher frequency and higher position of the reflecting ionosphere layer
The wavelength of a radio signal transmitted at the frequency of 75 MHz is:
A) 75 m.
B) 7.5 m.
C) 4 m.
D) 40 m.
Skin effect:
A) is the phenomenon where the apparent resistance of a wire decreases as
the frequency increases.
B) causes the apparent resistance of a wire to increase as the frequency
increases.
C) is purely a problem concerning DC transmitters where the resistance of
the aerial increases with frequency.
D) causes a reduction in power out but does not affect the transmitted beam
shape.
The frequency at which sky waves should least affect reception?
A) VLF
B) HF
C) MF
D) LF
The VHF Omnirange (VOR) uses the following wavelengths:
A) hectometric.
B) metric.
C) decimetric.
D) centimetric.
The minimum airborne equipment required for operation of a VHF direction finder is a:
A) VHF transmitter-receiver operating in the 118 MHz to 136 MHz range.
B) VHF receiver operating in the 118 MHz to 136 MHz range.
C) VHF compass operating in the 200 kHz to 1750 kHz range.
D) cathode-ray tube.
The high Altitude Radio Altimeter uses the following wavelengths:
A) hectometric.
B) metric.
C) myriametric.
D) decimetric.
For weather radar, the frequency 9375 MHz in X Band is preferable to C Band because:
A) It allows greater scanning rates.
B) It is not absorbed by heavy precipitations.
C) It better detects clouds contour and range is greater with the same
transmission power.
D) Its penetration power is higher.
Skip distance is the:
A) range from the transmitter to the first sky wave
B) thickness of the ionosphere
C) highest critical frequency distance
D) wavelength distance of a certain frequency
MF fading is most common:
A) during the day and during heavy rain.
B) at night due to the reception of both sky waves and ground waves.
C) during the day due to the reception of both sky waves and ground waves.
D) at night and during heavy rain.
Complete the following statement:... radio signals have a... range by... wave over... than over...
A) MF, shorter, sky, sea, land
B) MF, greater, ground, sea, land.
C) VHF, shorter, sky, sea, land.
D) MF, greater, ground, land, sea.
An aircraft transmits on HF from an altitude of 16000ft to an ATC which has its receiver aerial situated
on top of the control tower at a height of 120ft. At what range could the aircraft captain expect to
make radio contact?
A) 158,71 NM.
B) 1.044.500 ft.
C) 137,44 NM.
D) 171,8 NM.
The Low Altitude Radio Altimeter uses the following wavelengths:
A) metric.
B) centimetric.
C) myriametric.
D) decimetric.
21. The wavelength of a non-directional beacon (NDB) at a frequency of 300 kHz is:
A) 10 metres.
B) 100 metres.
C) 1 metre
D) 1000 metres.
The airborne weather radar uses the following wavelengths:
A) myriametric.
B) hectometric.
C) centimetric.
D) metric.
In aeronautics, the frequency range in which the reflection against the ionosphere layers is used, is:
A) SHF
B) HF
C) VHF
D) UHF
A Beat Frequency Oscillator:
A) is used to make radio reception less susceptible to interference.
B) is used to synchronise the radio receiver to the Beat Frequency of the transmitter.
C) is required only when a signal received which is an unmodulated carrier wave.
D) is required in order for a radio receiver to demodulate an amplitude
modulated signal.
The secondary Surveillance Radar (SSR) uses the following wavelengths:
A) myriametric.
B) centimetric.
C) hectometric.
D) decimetric.
The wavelength of a radio transmitted on frequency 121.95 MHz is:
A) 24.60 m
B) 2.46 m
C) 24.60 cm
D) 2.46 cm
The Fan Markers uses the following wavelengths:
A) hectometric.
B) myriametric.
C) metric.
D) centimetric.
What frequency band would a signal of 40cm wavelength belong to?
A) HF.
B) SHF.
C) VHF.
D) UHF.
A radio signal looses strength as range from the transmitter increases, this is called:
A) ducting
B) attenuation
C) propagation
D) refraction
The Microwave Landing System (MLS) uses the following wavelengths:
A) hectometric.
B) metric.
C) centimetric.
D) myriametric.
In the propagation of MF waves, the phenomenon of FADING is particularly found:
A) by day, due to the combination of sky and ground waves.
B) at night and when raining.
C) by day and when raining.
D) at night, due to the combination of the sky and ground waves.
An HF transmitter is tuned to a frequency that refracts from the E layer in the Ionosphere. The
maximum distance of the first returning skywave is:
A) 1500 km.
B) 599 NM.
C) 1500 NM.
D) 599 km.
The Automatic Direction Finder uses the following wavelengths:
A) decimetric.
B) hectometric or kilometric.
C) metric.
D) centimetric.
When an LF radio wave passes over the earth's surface it:
A) speeds up and is attenuated.
B) slows down and is attenuated.
C) slows down, picks up electrons and becomes stronger.
D) speeds up, picks up electrons and becomes stronger.
By day the ionosphere consists of:
A) 4
B) 3
C) 3
D) 4
layers
layers
layers
layers
between
between
between
between
60 and 400 km above the earth.
100 and 300 km above the earth.
60 and 400 km above the earth.
100 and 300 km above the earth.
In the response curve of an amplifier, the bandwidth is:
A) The
B) The
kHz
C) The
D) The
frequency band
frequency band
at each end.
frequency band
frequency band
corresponding to maximum gain less 3 decibels.
corresponding to maximum gain, increased by 10
corresponding to maximum gain.
corresponding to maximum gain less 20 decibels.