DUNFERMLINE HIGH SCHOOL
NATIONAL PHYSICS
HOMEWORK
01 Symbols and Plug
EQUATIONS:
Question 1 – 5 Marks
Copy and complete the following table.
COMPONENT
SYMBOL
COMPONENT
wire
resistor
switch
motor
cell
ammeter
battery
voltmeter
bulb
ohmmeter
SYMBOL
(5)
Question 2 – 6 Marks
Draw the following circuits:
a) A battery, bulb and resistor connected in series.
(2)
b) A battery and 3 bulbs connected in parallel.
(2)
c) A battery and bulb with an ammeter (to measure the current in the bulb) and a voltmeter (to measure the
supply voltage).
(2)
Question 3 – 2 Marks
There are several electrical hazards shown in the picture.
Identify two of the electrical hazards shown and for each explain why it is dangerous.
1
(2)
Question 4 – 1 Mark
Electric current is a flow of
A
charge
B
light
C
power
D
resistance
E
voltage.
(1)
Question 5 – 1 Mark
Which row in the table shows the circuit symbols for a resistor and a variable resistor?
(1)
Question 6 – 1 Mark
A student tests a resistor to find if it has an open circuit.
Which circuit should the student use?
(1)
2
Question 7 – 1 Mark
The diagram shows a plug wired correctly.
Which row in the table identifies terminal P and the colour of the insulation on wire Q?
(1)
Question 8 – 1 Mark
A student is wiring a plug.
Which row in the table shows the colour of the insulation for the live, neutral and earth wires?
(1)
3
Question 9 – 6 Marks
The flex of a mains appliance has a 3-pin plug fitted as shown.
The flex contains three wires - live, neutral and earth.
(a) Circle the correct answer for each of the questions about the wires.
(i) The colour of the insulation around the live wire is [blue, brown, green/yellow]
(1)
(ii) The colour of the insulation around the neutral wire is [blue, brown, green/yellow]
(1)
(iii) The [earth, live, neutral] wire is a safety device.
(1)
(b) Explain why the flex must be held in place by the cord grip.
(1)
(c) Another appliance has only two wires in its flex.
This appliance carries the following symbol.
(i) Name this symbol.
(1)
(ii) Which wire is not needed in this flex?
(1)
4
DUNFERMLINE HIGH SCHOOL
EQUATIONS:
NATIONAL PHYSICS
HOMEWORK
02 Circuits
V=IR
Question 1 – 4 Marks
A student’s games console stops working. She builds the circuit below to test the fuse in the plug.
(a) The student touches the metal probes together and bulb Y lights. She connects the metal probes to the fuse
for the games console. This time bulb Y does not light. What might be wrong with the fuse?
(1)
(b) The student sets up a new circuit including the component X.
X is used to vary the brightness of bulb Y. What is component X?
(1)
(c) The student adds an ammeter to the circuit in (b) to measure the current. Draw this new
circuit including the ammeter and the correct symbol for component X.
(2)
Question 2 – 2 Marks
The circuit shows how the headlights and front sidelights are wired in a car.
(a) Are the headlights connected in series or parallel with each other?
(1)
(b) Which switch or switches should be closed so that only the sidelights are on?
5
(1)
Question 3 – 6 Marks
A student sets up the following circuit.
(a) What is component Z?
(1)
(b) The student measures the voltage across the lamp with a voltmeter.
(i) Draw the symbol for a voltmeter.
(1)
(ii) Add your symbol to the circuit diagram above to show the voltmeter measuring the voltage across the
lamp.
(1)
(iii) The voltage across the lamp is 7 volts. What is the voltage across component Z?
(1)
(c) The student rearranges the circuit so that the components are connected as shown below.
The resistance of component Z is now reduced.
(i) State whether the total current in the circuit increases, decreases or stays the same.
(1)
(ii) Explain your answer.
(1)
6
Question 4 – 8 Marks
(a) Three identical lamps are shown in Circuit 1 below.
(i) The battery has a voltage of 12 volts and supplies a current of 1.2 ampere to the circuit.
Complete the table below to show the current in each lamp and the voltage across each lamp.
LAMP 1
LAMP 2
LAMP 3
Current (Amperes)
Voltage (Volts)
(3)
(ii) The three lamps and battery are now reconnected as shown in Circuit 2 below.
The current from the battery is now 0.3 ampere.
Complete the table below to show the current in each lamp and the voltage across each lamp.
LAMP 1
LAMP 2
LAMP 3
Current (Amperes)
Voltage (Volts)
(3)
(b) (i) Which of the circuits, Circuit 1 or Circuit 2, shown in (a) is similar to a household lighting
circuit?
(1)
(ii) Name an electrical appliance used in the home that requires two or more switches to be used in
series.
(1)
7
Question 5 – 4 Marks
Two identical lamps are connected to a 6·0 volt battery as shown in circuit 1.
(a) The battery supplies a current of 0·40 ampere to the circuit.
Complete the following table to show the current in each lamp and the voltage across each lamp.
(2)
(b) The two lamps are now connected as shown in circuit 2.
State the voltage of the battery required to light the lamps with the same brightness as in circuit 1.
(1)
(c) In which of the two circuits, circuit 1 or circuit 2, would lamp 2 still be on when lamp 1 is removed?
(1)
8
DUNFERMLINE HIGH SCHOOL
NATIONAL PHYSICS
EQUATIONS:
RT = R1 + R2
V=IR
HOMEWORK
03 V I R
Question 1 – 7 Marks
A student sets up circuit 1 to calculate the resistance of resistor R.
(a) Calculate the resistance of resistor R using the meter readings.
(4)
(b) The student then sets up circuit 2 to measure the resistance of R directly.
Write down the resistance of R, in ohms, obtained from circuit 2.
(1)
(c) The value obtained for the resistance of R using circuit 1 is more accurate than the value
obtained using circuit 2.
(i) Explain why circuit 1 gives a more accurate value for the resistance of R.
(1)
(ii) What change could be made in circuit 2 to give a more accurate value for the resistance of R?
(1)
9
Question 2 – 8 Marks
A student sets up the following circuit.
(a) Calculate the current in the 6 Ω resistor.
(3)
(b) Calculate the voltage across the 6 Ω resistor.
(3)
(c) The 32 Ω resistor is replaced by one of greater resistance.
How will this affect the voltage across the 6 Ω resistor?
Explain your answer.
(2)
10
Question 3 – 11 Marks
A variable power supply, an ammeter and a voltmeter are used to investigate how the current in a
thermistor changes as the voltage across the thermistor changes.
(a) Copy and complete the circuit diagram, including the ammeter and voltmeter, to show how the
current and voltage measurements are obtained.
(2)
(b) The current and voltage measurements obtained are used to draw the graph shown.
(i) What is the current in the thermistor when the voltage across the thermistor is 3.0 volts?
(1)
(ii) Calculate the resistance of the thermistor when the voltage across the thermistor is 3.0V.
(3)
(iii) By calculation, show how the resistance of the thermistor changes as the voltage across the
thermistor increases?
(5)
11
DUNFERMLINE HIGH SCHOOL
EQUATIONS:
RT = R 1 + R 2
NATIONAL PHYSICS
HOMEWORK
04 Resistance
V=IR
Questions 1 – 10 Marks
A student is given a piece of resistance wire 400 mm long and is asked to find its resistance.
Part of the circuit the student builds is shown below.
The student is also provided with a voltmeter and an ammeter.
(a) Redraw the diagram to show how the student should connect the meters to measure the resistance
of the wire.
(2)
(b) The student now uses measurements from the experiment to draw the following graph.
(i) Describe how the student uses the circuit to obtain the measurements for the graph.
(2)
(ii) Calculate the resistance of one metre of the wire.
(4)
(c) Two pieces of wire have resistances of 2.0Ω and 6.0Ω.
The wires are connected together as shown below.
Calculate the resistance between points X and Y.
(3)
12
Question 2 – 9 Marks
A post office contains an emergency alarm circuit. Each of three cashiers has an alarm switch fitted as
shown. Lamps come on and a bell sounds if an alarm switch is closed.
The circuit diagram for the alarm is shown.
(a) The alarm circuit is to be controlled by a master switch.
Which position (A, B, C or D) is most suitable for the master switch?
(1)
(b) Each lamp has a resistance of 8 Ω and the bell has a resistance of 12 Ω.
The circuit uses a 12 V supply.
(i) Calculate the total resistance of the alarm circuit.
(3)
(ii) Calculate the current from the supply when the alarm is operating.
(3)
(c) Brighter lamps are fitted in the alarm circuit.
Explain how this change affects the resistance of the circuit.
13
(2)
Question 3 – 8 Marks
The circuit below shows resistors connected as a potential divider.
Calculate the reading on the voltmeter
(a) when the switch is open;
(3)
(b) when the switch is closed.
(5)
14
DUNFERMLINE HIGH SCHOOL
EQUATIONS:
P = I2R
NATIONAL PHYSICS
P = V2 / R
HOMEWORK
P=IV
05 Power Energy
P=E/t
Question 1 – 13 Marks
Some resistors are labelled with a power rating as well as their resistance value.
This is the maximum power at which they can operate without overheating.
(a) A resistor is labelled 100 Ω, 5 W.
Calculate the maximum operating current for this resistor.
(3)
(b) Two resistors, each rated at 5 W are connected in parallel to a 12 V d.c. Supply.
They have resistances of 40 Ω and 20 Ω.
(i)
Calculate the total resistance of the circuit.
(3)
(ii)
Calculate the power produced in each resistor.
(5)
(iii)
State which, if any, of the resistors will overheat.
(1)
(c) The 12 V d.c. supply is replaced by a 12 V a.c. supply.
What effect, if any, would this have on your answers to part (b) (ii)?
15
(1)
Question 2 – 8 Marks
The electrical energy used by a 36 watt heater is measured with a joulemeter as shown.
The time taken to supply this energy is measured with a timer.
(a) The energy supplied is displayed on the joulemeter.
(i) Calculate the time taken to supply this energy.
(3)
(ii) The power supply provides direct current. Explain what is meant by direct current.
(1)
(b) Some household appliances are shown in the table.
(i) Complete the table using the correct power ratings from the list below.
60 watts
2800 watts
8000 watts
(3)
(ii) Some appliances have an earth wire. State the purpose of the earth wire.
16
(1)
Question 3 – 9 Marks
Four 20 Ω resistors R1, R2, R3 and R4 are connected in the form of a square ABCD.
A fifth resistor R5 of the same value is connected between A and C.
This arrangement of resistors is connected in a circuit as shown below.
The battery in the circuit has negligible internal resistance.
(a) Determine the total resistance between A and C.
(5)
(b) The switch S is now closed.
(i) In which of the resistors is the greatest power developed?
(1)
(ii) Calculate the value of this power.
(3)
17
DUNFERMLINE HIGH SCHOOL
EQUATIONS:
NATIONAL PHYSICS
HOMEWORK
06 Inputs Outputs
V=IR
Question 1 – 7 Marks
A strain gauge is an electrical device that is attached to an object. The strain gauge detects a change in the
shape of the object.
In the following diagrams, the strain gauge is shown attached to a piece of flexible metal.
When a force is applied to the end of the piece of metal, it bends.
When the metal is bent, the strain gauge also bends and its resistance changes.
The strain gauge is connected in series with a resistor, R, and a 12 V supply as shown in the circuit
diagram below.
(a) A student is asked to find the resistance of the strain gauge using a voltmeter and an ammeter.
Redraw the diagram to show how the student should connect the meters to measure the resistance of
the strain gauge.
(2)
(b) The student obtains the following results.
Voltmeter reading (V)
Ammeter reading (mA)
No Force Applied
8.40
80.0
Force Applied
8.49
78.0
Does the resistance of the strain gauge increase or decrease when the force is applied to the piece of
metal? You must justify your answer.
(2)
(c) Calculate the resistance of the resistor R.
(3)
18
Question 2 – 6 Marks
A thermocouple is used as a temperature sensor in a furnace. The thermocouple is attached to a chart
recorder that records the voltage generated by the thermocouple over a period of time.
(a) State the energy transfer that takes place in the thermocouple.
(1)
(b) Circle the correct word in the sentence below.
(1)
(c) The thermocouple is now connected to a circuit that has a digital display.
(i)
The resistance of the circuit is 750 ohms.
At a particular temperature, the thermocouple generates a voltage of 0.9 volt.
(ii)
Calculate the current in the thermocouple circuit.
(3)
Name a suitable output device that could be used for the digital display.
(1)
19
Question 3 – 7 Marks
A company makes sunglasses. The company uses a light meter to measure how much light passes
through different types of glass. The light meter contains an ammeter, an LDR and a 9 volt battery as
shown.
(a) For one type of glass, the current in the circuit is 0.01 ampere.
(i)
Calculate the resistance of the LDR.
(3)
(ii)
The intensity of the light shining on the LDR is increased.
(A)
State what happens to the resistance of the LDR.
(1)
(B)
State what happens to the current in the circuit.
(1)
(b) Three types of glass, X, Y and Z are tested as shown below to find out how much light passes
through each. The same source of light is used in all three tests.
Give two reasons why this is not a fair test.
(2)
20
Question 4 – 5 Marks
A 2.4 kΩ resistor and a variable resistor, R, are connected to a 6 volt d.c. supply as shown.
The supply has negligible internal resistance.
A voltmeter is used to measure the potential difference across the 2.4 kΩ resistor.
(a) Calculate the potential difference across the 2.4 kΩ resistor when the variable resistor, R, has a
value of 1.5 kΩ.
(3)
(b) The resistance of the variable resistor, R, is increased. Explain why the reading on the voltmeter
decreases.
(2)
21
DUNFERMLINE HIGH SCHOOL
NATIONAL PHYSICS
EQUATIONS:
P = V2 / R
V=IR
HOMEWORK
P = I2R
P = IV
07 Transistors
Question 1 – 6 Marks
The circuit shown can be used to build models of different electronic devices.
This is done by inserting a different component between X and Y for each model.
(a) Three models of electronic devices are built using this circuit. In each model one
component from the list below is placed between X and Y.
buzzer
capacitor
lamp
LDR
LED
thermistor
Complete the table to show which component is used for each device.
(b) (i)
(ii)
(3)
Name component Q.
(1)
What is the purpose of component Q in this circuit?
(1)
(c) What is the purpose of resistor R in this circuit?
(1)
22
Question 2 – 9 Marks
The circuit shown below is used to investigate the behaviour of component X.
(a) (i) What is the name of component X?
(1)
(ii) What name is given to the arrangement of the two series resistors R1 and R2 connected across the 9.0
V supply?
(1)
(b) By using different values of resistor R1, different voltages are applied to the input of X.
The graph below shows how the current through X changes as the voltage applied to the input is altered.
(i) What is the reading on the voltmeter when device X starts to conduct?
(1)
(ii) Calculate the value of resistor R1 which is required to obtain this voltage.
(3)
23
c)
Component X is now connected into the circuit below to switch on an emergency lamp when it
becomes dark.
The table below shows the resistance of the LDR in light and in dark.
Explain how this circuit operates to switch on the emergency, lamp.
24
(3)
Question 3 – 12 Marks
A hotel owner decides to install three lamps on the drive between the hotel and the street.
The circuit diagram below shows how the lamps are connected to the mains supply.
Each lamp has a rating of 230 V, 299 W.
(a) Explain why the lamps must be connected in parallel.
(1)
(b) Calculate the resistance of each lamp.
(3)
(c) Calculate the current drawn from the supply when all three lamps are operating.
(4)
(d) The lamps are connected to the circuit shown below so that they come on automatically when it gets
dark.
(i) Identify components labelled X and Y
(2)
(ii) Component Y switches on when the voltage V1 reaches 2.4 V
Switch S is closed when there is a current in the relay.
Explain how this circuit will switch the lamps on when it becomes dark.
25
(3)
DUNFERMLINE HIGH SCHOOL
NATIONAL PHYSICS
EQUATIONS:
RT = R1 + R2 + …
V=IR
HOMEWORK
08 Logic Gates
Question 1 – 7 Marks
An electronic system is used to control a lift. When a floor has been selected, two checks are made:
there are no obstructions to the doors; the lift is not overloaded.
Part of the circuit is shown below.
The logic states are as shown for the floor selector, the sensors and the door mechanism.
(a) Name logic gate X.
(b) (i)
(ii)
(1)
Gate Y is a NOT gate. Draw the symbol for a NOT gate.
(1)
Copy and complete the truth table for a NOT gate.
(1)
(c) (i)
(ii)
State the logic levels needed at P, Q and R to close the lift doors.
(3)
What output device could be used for the door opening and closing mechanism?
(1)
26
Question 2 – 5 Marks
A pedestrian crossing at a set of traffic lights has an electronic control system to operate the
“green man” light. Part of the system is shown.
Input A is from the traffic lights and gives a logic 1 when the red light only is on, and a logic 0
at other times.
Input B is operated by pedestrians when they want to cross.
(a) State a suitable input device to be used by the pedestrians to activate the “green man” light.
(1)
(b) The “green man” light comes on when the red traffic light, only, is on and the crossing is
operated by a pedestrian. What type of logic gate should be used at position X?
(1)
(c) The “green man” light consists of a number of LEDs.
(i)
Draw the symbol for an LED.
(1)
(ii)
Why does each LED need a series resistor?
(1)
(d) The “green man” light has to stay on long enough for the pedestrian to cross.
This crossing has a display to show pedestrians the number of seconds the “green man”
light will remain on.
State an output device that could be used to display this time.
27
(1)
Question 3 – 10 Marks
The exit of an underground car park has an automatic barrier. The barrier rises when a car
interrupts a light beam across the exit and money has been put into the pay machine. The barrier
can also be operated by using a manual switch.
The light beam is directed at an LDR that is connected as shown in the circuit below.
(a) Calculate the voltage across the LDR when its resistance is 15 kΩ
(3)
(b) Part of the control circuit for the automatic barrier is shown below.
When a car interrupts the light beam, the logic level at P changes from logic 0 to logic 1.
When money is put into the pay machine, the logic level at Q changes from logic 0 to logic 1.
When the manual switch is operated, the logic level at S changes from logic 0 to logic 1.
(i)
Name logic gate X.
(1)
(ii)
Name logic gate Y.
(1)
(iii)
Complete the truth table on the next page for the control circuit shown, by filling in the values of
the logic levels at R and T.
28
(4)
(iv)
Describe a situation where it would be necessary to operate the barrier by using the
manual switch.
(1)
Question 4 – 5 Marks
A bus is fitted with a buzzer that sounds only when the bus is reversing. Part of the circuit that operates the
buzzer is shown.
The output from the gearbox switch is high (logic 1) when the bus is reversing.
(a) Name logic gate G.
(1)
(b) The table shows the different possible combinations of logic levels (0 or 1) for input P and input Q to gate
G.
Complete the last column of the table by drawing the output R from gate G for each combination of
inputs.
(4)
29
DUNFERMLINE HIGH SCHOOL
NATIONAL PHYSICS
EQUATIONS:
%efficiency =
Q=It
HOMEWORK
09 Electromagnetism
x 100
Question 1 - 5 Marks
(a) A conductor is moved between the poles of a magnet.
The diagrams show the positions of the pointer on a centre-zero voltmeter when the conductor is
moved as shown.
The diagrams below show other situations in which the conductor is moved between the poles of
the magnet.
In each case, show on the diagram the position of the pointer while the conductor is moving.
(3)
(b) The diagram shows how a bicycle dynamo is constructed.
Use the names given below to label the three main parts of the dynamo.
coil
iron core
magnet
30
(2)
Question 2 - 6 Marks
A car fan uses a battery powered electric motor. The diagram below shows
the apparatus used to investigate the effect of current on the speed of the electric motor.
(a) The graph shows the relationship between speed and current during the investigation.
(i) The current is changed using the variable speed control.
What happens to the current when the resistance of the variable speed controller is reduced?
(1)
(ii) The settings of the variable speed control use different combinations of identical resistors, as
shown.
(A) To which position should the variable speed control be set to achieve maximum speed?
(1)
(B) Justify your answer.
(2)
(b) The electric motor is shown on the next page.
(i) Explain the purpose of the commutator.
(1)
(ii) Why are the brushes made of carbon rather than metal wire?
(1)
31
Question 3 - 6 Marks
A student makes a device to measure the speed of moving air.
Moving air pushes the plastic cups round and this turns the metal rod.
A bar magnet is attached to the rod as shown in the diagram.
(a) Explain why a reading is shown on the voltmeter when the cups move.
(2)
(b) What happens to the voltmeter reading when the air speed increases?
(1)
(c) Suggest two changes which could he made to the apparatus to give a bigger reading on the
voltmeter.
(2)
(d) Explain, in terms of electron flow, what is meant by a.c.
32
(1)
Question 4 - 8 Marks
A wind generator is used to charge a 12 V battery. The charging current depends on the wind speed.
The graph shows the charging current at different wind speeds.
(a) During one charge of the battery, the wind speed is constant at 15 m/s.
During this time a charge of 3900 C is transferred to the battery.
Calculate the time taken to transfer this charge to the battery.
(4)
(b) At another wind speed the generator has an output power of 120 W and is 25% efficient.
Calculate the input power to the generator.
(3)
(c) A bicycle has a small generator called a dynamo. The dynamo contains a magnet which spins
near a coil of wire.
When the magnet spins, a voltage is induced in the coil.
State two factors that affect the size of the induced voltage.
33
(2)
DUNFERMLINE HIGH SCHOOL
NATIONAL PHYSICS
EQUATIONS:
P=E/t
P=IV
HOMEWORK
% efficiency =
10 Renewables
x 100
Question 1 – 4 Marks
A thermal power station has an efficiency of 42%. A combined heat and power station is more
efficient; it uses heat to produce hot water for homes as well as generating electrical energy. The
energy output for each power station is shown in the diagrams below.
(a) (i)
(ii)
Calculate the percentage of waste heat for the thermal power station.
(1)
Calculate the total percentage useful energy output of the combined heat and power station.
(1)
(b) A combined heat and power station saves energy in the power industry.
(i)
Describe one method of saving energy in the home.
(1)
(ii)
Describe one method of saving energy in transport.
(1)
34
Question 2 – 7 Marks
The pie chart shows the estimated use of the world's main energy sources for the year 2000.
(a) Use the names of the energy sources given in the pie chart to complete the table.
(3)
(b) Use the pie chart to calculate the total percentage of energy supplied by fossil fuels.
(2)
(c) Why is it important to find sources of energy other than fossil fuels?
(1)
(d) Name one renewable source of energy that is not mentioned in the pie chart.
(1)
35
Question 3 – 10 Marks
A traffic information sign is located in a remote area. The sign is supplied with energy by both a
panel of solar cells and a wind generator. The panel of solar cells and the wind generator are
connected to a rechargeable battery.
(a) One square metre of solar cells can generate up to 60 watts.
The panel of solar cells has an area of 0·6 square metres.
(i)
State the energy change that takes place in the solar cells.
(1)
(ii)
Calculate the maximum power produced by the panel of solar cells.
(3)
(b) The following table shows the power produced by the wind generator at different wind speeds.
Wind speed (m/s)
Power output of wind
generator (watts)
4
16
8
32
12
16
64
20
80
(i)
Suggest the power produced when the wind speed is 12 metres per second.
(ii)
At a wind speed of 20 metres per second the voltage produced by the wind generator
(1)
is 32 volts.
Calculate the current produced by the wind generator.
(4)
(c) Explain why a rechargeable battery is also required to supply energy to the traffic information sign.
(1)
36
Question 4 – 8 Marks
An underwater generator is designed to produce electricity from water currents in the sea.
The output power of the generator depends on the speed of the water current as shown in Graph 1.
The speed of the water current is recorded at different times of the day shown in Graph 2.
(a) (i)
(ii)
State the output power of the generator at 09:00.
(1)
State one disadvantage of using this type of generator.
(1)
(b) The voltage produced by the generator is stepped-up by a transformer.
At one point in the day the electrical current in the primary coils of the transformer is 800A and
the voltage is 1800V.
The transformer is 92% efficient.
(i)
Calculate the output power of the transformer at this time.
(5)
(ii)
State one reason why a transformer is not 100% efficient.
(1)
37
DUNFERMLINE HIGH SCHOOL
NATIONAL PHYSICS
EQUATIONS:
Q=It
P=IV
HOMEWORK
11 Transformers
Question 1 – 6 Marks
Electrical power is distributed by the National Grid system.
Transformers are used in this grid system.
(a) State why transformers are used in the grid.
(1)
(b) The voltages required at various stages of the grid system are shown.
A transformer transfers power from the National Grid to heavy industry.
The primary coil of the transformer has 7500 turns.
(i)
State the voltage input at the primary coil.
(1)
(ii)
State the voltage output at the secondary coil.
(1)
(iii)
Calculate the number of turns in the secondary coil.
(3)
38
Question 2 – 8 Marks
In a car battery charger, a transformer is used to step voltage down from 230 V to 12 V.
The stepped down voltage is converted to d.c. using a converter. The circuit is shown below.
(a) There are 1725 turns on the primary coil.
Calculate the number of turns on the secondary coil.
(b) (i)
(ii)
(3)
What do the initials d.c. stand for?
(1)
Explain what d.c. means in terms of electron flow in a circuit.
(1)
(c) The charger delivers a current of 250 mA to the battery for a period of 4 hours.
Calculate the charge delivered to the battery during this time.
(3)
Question 3 – 10 Marks
The following circuit shows a method of transmitting power over long distances.
The table shows the readings on some of the meters.
V1
12 V
A1
120 mA
V3
8.8 V
A3
210 mA
(a) Why must a.c. be used in this circuit
(2)
(b) All lamps are identical. Calculate the power of lamp Q.
(3)
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(c) Transformer Y has 900 turns in the primary coil and 30 turns in the secondary coil.
Calculate the reading on voltmeter V2 assuming the transformer is 100% efficient.
(3)
(d) Is the reading on A2 larger, smaller or the same as the reading on A3?
Explain your answer.
(2)
Question 4 – 6 Marks
A mobile phone charging unit contains a transformer.
The transformer circuit is shown below.
(a) Calculate the secondary voltage of the transformer.
(3)
(b) When the phone is being charged the current in the primary coil of the transformer is 24 mA.
Calculate the current in the secondary coil of the transformer.
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(3)
DUNFERMLINE HIGH SCHOOL
NATIONAL PHYSICS
EQUATIONS:
P=E/t
P=IV
HOMEWORK
12 Specific Heat
EH = cmΔT
Question 1 – 4 Marks
A house is designed to conserve as much energy as possible.
(a) Heat energy can be lost from the house by a variety of means.
Insulation is used to reduce heat loss.
Match the correct type of insulation given in the word bank with each type of heat loss.
Use each answer once only.
foil-backed plasterboard
TYPE OF HEAT LOSS
double glazing
loft insulation
CORRECT INSULATION
Conduction
Convection
Radiation
(3)
The temperature in the house is kept at a constant value while the temperature outside changes.
The graph shows the temperature inside the house and the temperature outside the house over
a 24 hour period.
(b) Write down the time at which heat loss from the house is greatest.
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(1)
Question 2 – 9 Marks
An electric storage heater contains a heating element, thermal blocks and insulation as shown in the
diagram.
The heating element heats the thermal blocks during the night.
(a) Between midnight and 6.00 am, 8.64x107 J of energy are supplied to the heating element.
(i)
Calculate the power rating of the heating element.
(3)
(ii)
The total mass of the thermal blocks in the heater is 144 kg and the specific heat capacity
of the thermal blocks is 2625 J/kgºC.
Calculate the maximum possible rise in the temperature of the thermal blocks between
midnight and 6.00 am.
(iii)
(3)
Explain why the actual temperature rise of the blocks is less than the value calculated in (a)(ii).
(1)
(b) Why is there insulation between the thermal blocks and the outer casing of the heater?
(1)
(c) During the day, heat energy stored in the heater is released into the room.
State one way in which heat is transferred to the surroundings from this heater.
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(1)
Question 3 – 8 Marks
A student sets up the apparatus shown to measure the specific heat capacity of an aluminium block.
The student obtains the following results:
mass of aluminium block
m = 1.4 kg
temperature change
ΔT = 11ºC
time taken
t = 5.0 minutes
heater current
I = 4.5 A
heater voltage
V= 12 V
(a) Show, by calculation, that 16 200 J of electrical energy are supplied to the heater in 5.0 minutes. (3)
(b) (i)
Assuming all of the electrical energy is transferred to the aluminium block as heat energy,
calculate the value of the specific heat capacity of aluminium obtained from this
experiment.
(ii)
(3)
The accepted value of the specific heat capacity of aluminium is 902 J/kg ºC.
(A) Give a reason for the difference between your answer in (b)(i) and this value.
(1)
(B) How could the experiment be improved to reduce this difference?
(1)
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Question 4 – 7 Marks
A mains operated air heater contains a fan, driven by a motor, and a heating element.
Cold air is drawn into the heater by the fan. The air is heated as it passes the heating element.
The circuit diagram for the air heater is shown.
(a) (i)
(ii)
What is the voltage across the heating element when the heater is operating?
(1)
What type of circuit is used for the air heater?
(1)
(b) The following data relates to the heater when the fan rotates at a particular speed.
mass of air passing through per second
0.4 kg
energy supplied to air per second
2500J
specific heat capacity of air
1000 J/kg°C
(i)
Calculate the increase in air temperature.
(3)
(ii)
The motor is adjusted to rotate the fan at a higher speed.
This draws a greater mass of air per second through the heater.
Explain any difference this causes to the temperature of the hot air.
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(2)
DUNFERMLINE HIGH SCHOOL
EQUATIONS:
NATIONAL PHYSICS
HOMEWORK
13 Gas Laws
P=F/A
Question 1 – 9 Marks
A technician designs the apparatus shown in the diagram to investigate the relationship between
the temperature and pressure of a fixed mass of nitrogen which is kept at a constant volume.
(a) The pressure of the nitrogen is 130 kPa when its temperature is 25ºC. The temperature of the nitrogen
rises to 55 °C. Calculate the new pressure of the nitrogen in the flask.
(3)
(b) Explain, in terms of the movement of gas molecules, what happens to the pressure of the nitrogen as its
temperature is increased.
(2)
(c) The technician has fitted a safety valve to the apparatus. A diagram of the valve is shown below.
The piston of cross-sectional area 6.0x10-6 m2 is attached to the spring. The piston is free to move along
the tube. The following graph shows how the length of the spring varies with the force exerted by the
nitrogen on the piston.
Calculate the force exerted by the nitrogen on the piston when the reading on the pressure gauge is
2.45x105 Pa.
(3)
(d) The technician decides to redesign the apparatus so that the bulb of the thermometer is placed inside the
flask. Give one reason why this improves the design of the apparatus.
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(1)
Question 2 – 11 Marks
The apparatus used to investigate the relationship between volume and temperature of a fixed mass of air is
shown.
The volume of the trapped air is read from the scale on the syringe. The temperature of the trapped air is
altered by heating the water in the beaker. It is assumed that the temperature of the air in the syringe is the
same as that of the surrounding water. The pressure of the trapped air is constant during the investigation.
Readings of volume and temperature for the trapped air are shown.
Temperature / °C
20
40
60
80
Volume / ml
20.5
21.9
23.3
24.7
(a) Using all the data, establish the relationship between temperature and volume for the
trapped air.
(5)
(b) Calculate the volume of the trapped air when the temperature of the water is 65 °C.
(3)
(c) Use the kinetic model of gases to explain the change in volume as the temperature increases in this
investigation.
(3)
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Question 3 – 7 Marks
The cylinder of a bicycle pump has a length of 495 mm as shown in the diagram.
The outlet of the pump is sealed.
The piston is pushed inwards until it is 220 mm from the outlet.
The initial pressure of the air in the pump is 15x105 Pa.
(a) Assuming that the temperature of the air trapped in the cylinder remains constant, calculate
the final pressure of the trapped air.
(3)
(b) State one other assumption you have made for this calculation.
(1)
(c) Use the kinetic model to explain what happens to the pressure of the trapped air as its
volume decreases.
(3)
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ELECTRICITY AND ENERGY NATIONAL HOMEWORK
HOMEWORK
TOTAL MARK
01 Symbols and Plug
/ 24
02 Circuits
/ 24
03 V I R
/ 26
04 Resistance
/ 28
05 Power Energy
/ 30
06 Inputs Outputs
/ 26
07 Transistors
/ 28
08 Logic Gates
/ 27
09 Electromagnetism
/ 26
10 Renewables
/ 29
11 Transformers
/ 30
12 Specific Heat Capacity
/ 28
13 Pressure Gas Laws
/ 27
COMMENTS
48