DC CIRCUITS – BASIC ELECTRICITY
1. A conductor has a radius of 0.1625 inch. What is the area in circular mils?
a. 26,406.25
c. 100,000
b. 82,957.68
d. 105,625
2. The specific resistant ρ depend upon
a. The area of cross section and the length of the conductor
b. The material of the conductor, its area of the cross section and length
c. The nature of the material of the conductor only
d. The area of the cross-section of the conductor
3. The condition in Ohm’s law is that
a. Ratio V/I should be constant
b. Current should be proportional to voltage
c.
d.
The temperature should remain constant
The temperature should vary
4. Heating effect of current has an undesirable side effect in
a. Electric oven
b. Immersion heater
c.
d.
Electric iron
Vacuum cleaner
5. A wire has a resistance of 1Ω. If the length is increased four times and the area is doubled the original, find the
new resistance of the wire
a. 5 Ω
c. 1 Ω
b. 2 Ω
d. 0.5 Ω
6. An aluminium wire has a diameter of 2mm. What must be the diameter of copper wire of the same resistance and
length as aluminium?
a. 1.33mm
c. 1.56mm
b. 1.45mm
d. 1.75mm
7. A copper wire is drawn down such that its length is doubled but the volume remains the same, what is the new
resistance of the wire?
a. R
c. 2R
b. R/2
d. 4R
8. The resistance of a copper wire at 30°C is 50 Ω. If the temperature coefficient of copper at 0°C is 0.00427, what is
the resistance at 100°C
a. 72.26 Ω
c. 54.25 Ω
b. 63.24 Ω
d. 58.15 Ω
9. What is the total resistance of eleven 33kΩ resistors connected in parallel?
a. 33 kΩ
c. 363 kΩ
b. 3 kΩ
d. 11 kΩ
10. Three resistance of 4, 9, and 11 ohms are connected in series and then in parallel. Find the effective resistance for
series connection
a. 15Ω
c. 24Ω
b. 20Ω
d. 13Ω
11. Three resistors of 3, 6, and Z ohms, respectively are connected in parallel across a constant current source of 10A.
Find the value of Z if this resistor draws 2A current
a. 3
c. 4
b. 6
d. 8
12. A voltage divider circuit of two resistors is designed with a total resistance of the two resistors equal to 100 ohms.
If the output voltage is 20% of the input, what are the values of the 2 resistors in the circuit?
a. 15 and 85
c. 10 and 90
b. 20 and 80
d. 2 and 98
13. Three resistors A, B, and C are connected in series to a 120 V supply. If the resistor A=50 ohms and the voltage
across resistor B=40V when the current is 1/2A, what is the resistance of resistor C in ohms?
a. 105
c. 110
b. 90
d. 100
14. The voltage applied across an electric press was reduced by 50%. The power consumed by the press will be
reduced to
a. 25%
c. 60%
b. 50%
d. 75%
15. A walkman has 4 –AA batteries. The combination has a capacity of 200 watt-sec. How long will it take to
discharge if walkman consumes 10mA at 6V?
a. 55.6 min
c. 45.6 min
b. 65.6 min
d. 75.6 min
16. One KWHR is equal to _____ BTU
a. 360
b. 3413
c.
d.
3600
1000
17. In a certain process water is heated at a rate of 2liters per minute. The water enters an electric heater at 25°C and
exits at 50°C. Assuming no heat loss, calculate the wattage of the heater
a. 2420
c. 6520
b. 3488
d. 5125
18. How is the storage battery rated in capacity
a. Volts
b. Watts
c.
d.
Amperes
Ampere-hour
19. Which of the following characteristic of the plates of the battery will the Ampere-Hour of the battery depends on?
a. Distance
c. Strength
b. Area
d. Thickness
20. The terminal voltage of a battery is 11.8V when delivering 20W of power to an external resistor. If the battery has
an emf of 15V, find the internal resistance of the battery
a. 1.96 ohms
c. 1.68 ohms
b. 1.89 ohms
d. 1.75 ohms
DC CIRCUITS – ELECTROMAGNETISM
21. It is the unconventional unit of mmf in the CGS system
a. Unit pole
b. Statvolts
c.
d.
Gilberts
Ampere turns
22. What is the counterpart of magnetic flux in an electric circuit?
a. Voltage
b. Current
c.
d.
Resistance
Conductance
23. The law that induces emf and current always opposes the cause producing them was discovered by
a. Faraday
c. Lenz
b. Maxwell
d. Ohm
24. When the current in a wire is 5A, the flux 3 meters from the wire is 30mWb. If the current is decreased to 4A,
what will be the flux?
a. 24 mWb
c. 19.2 mWb
b. 37.5 mWb
d. 46.88 mWb
25. A straight conductor 100 cm long and carrying a current of 40A lies perpendicular to a magnetic field of 1.5
Wb/m2. What is the mechanical power in watts required to move the conductor at a uniform speed of 5 m/s?
a. 390 W
c. 330 W
b. 300 W
d. 360 W
26. A solenoid has an inductance of 1.58mH. How many turns of wire does it have if the solenoid is 25cm long and
its radius is 2.5 cm?
a. 160,000 turns
c. 400 turns
b. 350 turns
d. 600 turns
27. An iron core has a cross sectional area of 10-3square meter and mean circumference of 1 meter. The relative
permeability of the material is 500 and the number of turns is 200. Determine the current required to set up a flux
of 0.001 weber.
a. 7.54 A
c. 8.19 A
b. 7.96 A
d. 8.47 A
28. A 1m long conductor is moved in a field of density 1 Wb/m2 at a velocity of 30 m/s. What is the emf induced if
the motion is perpendicular to the field?
a. 20V
c. 15V
b. 30V
d. 25V
29. Find the induced emf of a coil with 50 turns and with changing flux of 3 Wb/sec
a. 1.5V
c. 150V
b. 15V
d. 16.7V
30. Two identical coupled coils have an equivalent inductance of 80mH when connected in series aiding and 35mH in
series opposing. Find the coefficient of coupling.
a. 0.39
c. 0.5
b. 0.43
d. 0.64
DC CIRCUITS – ELECTROSTATICS
31. An 800 W electric iron operates on 110V. How many electrons pass through the iron per second
a. 4.54 x 1019
c. 70.4 x 106
9
b. 6.4 x 10
d. 3.25 x 1019
32. An equal number of electrons is placed on two metal spheres 3 cm apart in air. How many electrons are on each
sphere if the resultant force is 4kN?
a. 1.47 x 1014
c. 1.25 x 1014
b. 1.33 x 1014
d. 1.40 x 1014
33. The area of one plate of a two plate mica capacitor is 0.0025 m2 and the separation between plates is 0.02 m. If the
dielectric constant of mica is 5, what is the capacitance of the capacitor?
a. 5.53 µF
c. 7.74 µF
b. 5.53 pF
d. 7.74 pF
34. A multi-plate capacitor is made up of 501 sheets of aluminium 25cm x 30cm with an insulation of paraffin paper
0.0015 cm thick. What is the capacitance in microfarads of the capacitor (k for paraffin paper is 3)?
a. 50
c. 35
b. 55
d. 67
35. Two capacitors in series are charged across a 24V source. If C1 is 12 picofarads, and the voltage across it is 6V,
find C2
a. 6 pF
c. 2 pF
b. 8 pF
d. 4 pF
36. A 220 V bulb draws a current of 10A. How much in kilocoulombs will pass through the bulb in two hours period?
a. 7.2
c. 36
b. 3.6
d. 72