Electricity

1. What is the SI unit of electric current?
A) Volt
B) Ampere
C) Ohm
D) Coulomb
Answer: B) Ampere

2. Which instrument measures electric current in a circuit?
A) Voltmeter
B) Ammeter
C) Galvanometer
D) Rheostat
Answer: B) Ammeter

3. How does a switch function in an electric circuit?
A) Generates electricity
B) Opens or closes the circuit
C) Increases resistance
D) Decreases voltage
Answer: B) Opens or closes the circuit

4. What constitutes the flow of charges in a metallic wire?
A) Protons
B) Neutrons
C) Electrons
D) Atoms
Answer: C) Electrons

5. What is the unit of electric charge?
A) Coulomb
B) Volt
C) Joule
D) Watt
Answer: A) Coulomb

6. What is the value of 1 Coulomb of charge in terms of electrons?
A)

1.6×10181.6 \times 10^{18}

 electrons
B)

6×10186 \times 10^{18}

electrons
C)

9×10189 \times 10^{18}

electrons
D)

3.2×10183.2 \times 10^{18}

electrons
Answer: B)

6×10186 \times 10^{18}

electrons

7. Which scientist is the Ampere unit named after?
A) Alessandro Volta
B) James Watt
C) Andre-Marie Ampere
D) Georg Simon Ohm
Answer: C) Andre-Marie Ampere

8. In which direction is conventional current considered to flow in a circuit?
A) From positive to negative terminal
B) From negative to positive terminal
C) Both directions simultaneously
D) Perpendicular to the circuit
Answer: A) From positive to negative terminal

9. The potential difference is defined as the work done to move a unit charge between two points. What is its SI unit?
A) Ampere
B) Ohm
C) Volt
D) Joule
Answer: C) Volt

10. Which device measures potential difference across two points in a circuit?
A) Ammeter
B) Galvanometer
C) Voltmeter
D) Multimeter
Answer: C) Voltmeter

11. What is the formula for Ohm’s Law?
A) 

I=V/RI = V/R

B)

R=V×IR = V \times I

C)

V=R/IV = R/I

D)

R=I/VR = I/V

Answer: A)

I=V/RI = V/R

12. What property of a material opposes the flow of electric current?
A) Conductance
B) Capacitance
C) Resistance
D) Potential difference
Answer: C) Resistance

13. Which unit represents electrical resistance?
A) Watt
B) Coulomb
C) Ohm
D) Volt
Answer: C) Ohm

14. What is the resistance of a wire directly proportional to?
A) Cross-sectional area
B) Length of the wire
C) Voltage applied
D) Electric current
Answer: B) Length of the wire

15. Which of the following is an alloy with high resistivity?
A) Silver
B) Copper
C) Nichrome
D) Aluminum
Answer: C) Nichrome16. What is the resistivity of a good conductor like copper?

A)

10−8 Ω m10^{-8} \, \Omega \, m

B)

10−6 Ω m10^{-6} \, \Omega \, m

C)

10−3 Ω m10^{-3} \, \Omega \, m

D)

10−12 Ω m10^{-12} \, \Omega \, m

Answer: A)

10−8 Ω m10^{-8} \, \Omega \, m

17. What happens to the resistance of a wire if its diameter is doubled, keeping the length constant?
A) Increases four times
B) Decreases four times
C) Doubles
D) Halves
Answer: B) Decreases four times

18. If the length of a conductor is doubled, what happens to its resistance?
A) Doubles
B) Halves
C) Remains the same
D) Reduces to one-fourth
Answer: A) Doubles

19. Which of these materials is used for the filament of electric bulbs?
A) Copper
B) Tungsten
C) Nichrome
D) Aluminum
Answer: B) Tungsten

20. What is the SI unit of resistivity?
A)

Ω m\Omega \, m

B)

Ω/m\Omega /m

Ω/m
C)

Ω/m2\Omega/m^2

D)

Ω/m3\Omega/m^3

Answer: A)

Ω m\Omega \, m

21. What is the resistance of a 1200 W heater operating at 220 V?
A)

44 Ω44 \, \Omega

B)

40 Ω40 \, \Omega

C)

60 Ω60 \, \Omega

D)

20 Ω20 \, \Omega

Answer: B)

40 Ω40 \, \Omega

22. In a parallel circuit, how is the total resistance related to the individual resistances?
A) Equal to the sum of resistances
B) Less than the smallest resistance
C) Equal to the largest resistance
D) Greater than the sum of resistances
Answer: B) Less than the smallest resistance

23. Which type of circuit is used in domestic wiring?
A) Series
B) Parallel
C) Open
D) Mixed
Answer: B) Parallel

24. What happens to the total resistance if resistors are connected in series?
A) Decreases
B) Remains the same
C) Increases
D) Becomes zero
Answer: C) Increases

25. What does a fuse wire prevent?
A) High current flow
B) Voltage fluctuations
C) Power loss
D) Short circuits
Answer: A) High current flow

26. What is the formula to calculate power in an electric circuit?
A)

P=VIP = VI

B)

P=V/IP = V/I

C)

P=I2/RP = I^2/R

D)

P=IRP = IR

Answer: A)

P=VIP = VI

27. A 100 W bulb operates at 220 V. What is its resistance?
A)

242 Ω242 \, \Omega

B)

484 Ω484 \, \Omega

C)

100 Ω100 \, \Omega

D)

22 Ω22 \, \Omega

22Ω
Answer: B)

484 Ω484 \, \Omega

28. What determines the heat produced in a resistor?
A) Square of current
B) Resistance only
C) Voltage only
D) Time only
Answer: A) Square of current

29. How does increasing the cross-sectional area of a conductor affect its resistance?
A) Increases resistance
B) Decreases resistance
C) No change
D) Resistance becomes infinite
Answer: B) Decreases resistance

30. Which of these has the highest resistivity?
A) Copper
B) Nichrome
C) Iron
D) Glass
Answer: D) Glass

31. What is the formula for Joule’s law of heating?
A)

H=VItH = VIt

B)

H=I2RtH = I^2Rt

C)

H=V2t/RH = V^2t/R

D) All of these
Answer: D) All of these

32. What is the commercial unit of electric energy?
A) Joule
B) Watt
C) Kilowatt-hour
D) Ohm
Answer: C) Kilowatt-hour

33. How is a voltmeter connected in a circuit?
A) In series
B) In parallel
C) Diagonally
D) Any way
Answer: B) In parallel

34. Which of the following devices is used to regulate current in a circuit?
A) Voltmeter
B) Ammeter
C) Rheostat
D) Galvanometer
Answer: C) Rheostat

35. What is the reciprocal of resistance called?
A) Resistivity
B) Conductivity
C) Conductance
D) Capacitance
Answer: C) Conductance

36. What is the SI unit of power?

A) Watt
B) Joule
C) Ohm
D) Volt
Answer: A) Watt

37. The rate of flow of electric charges in a circuit is called?
A) Voltage
B) Resistance
C) Current
D) Power
Answer: C) Current

38. How much energy is transferred when a 100 W device operates for 2 hours?
A) 100 Wh
B) 200 Wh
C) 0.1 kWh
D) 0.2 kWh
Answer: B) 200 Wh

39. Which of these is NOT an application of the heating effect of current?
A) Electric bulb
B) Electric heater
C) Electric motor
D) Toaster
Answer: C) Electric motor

40. What is the purpose of an electric fuse?
A) Increase voltage
B) Increase resistance
C) Prevent excessive current
D) Store charge
Answer: C) Prevent excessive current

41. In a circuit, when current doubles, how does the heat generated change?
A) Doubles
B) Triples
C) Quadruples
D) Halves
Answer: C) Quadruples

42. Which material is most suitable for making the filament of an electric bulb?
A) Copper
B) Aluminum
C) Tungsten
D) Iron
Answer: C) Tungsten

43. Which of the following is the formula to calculate electric energy?
A)

P=VIP = VI

B)

E=P×tE = P \times t

C)

I=V/RI = V/R

D)

R=V/IR = V/I

Answer: B)

E=P×tE = P \times t

44. A combination of resistors in parallel provides:
A) Greater resistance than series
B) Lesser resistance than series
C) Same resistance as series
D) Zero resistance
Answer: B) Lesser resistance than series

45. The resistance of an electric component remains constant. If the potential difference is halved, what happens to the current?
A) Halved
B) Doubled
C) No change
D) Tripled
Answer: A) Halved

46. Which of these resistors will offer the least resistance?
A) Long and thin wire
B) Short and thick wire
C) Long and thick wire
D) Short and thin wire
Answer: B) Short and thick wire

47. What is the total resistance of two resistors,

R1=2 ΩR_1 = 2 \, \Omega and

R2=3 ΩR_2 = 3 \, \Omega  connected in series?
A)

1.2 Ω1.2 \, \Omega

B)

5 Ω5 \, \Omega

C)

0.6 Ω0.6 \, \Omega

D)

10 Ω10 \, \Omega

Answer: B)

5 Ω5 \, \Omega

48. Which quantity is measured in kilowatt-hour?
A) Power
B) Energy
C) Current
D) Resistance
Answer: B) Energy

49. The efficiency of an electric circuit can be increased by:
A) Using higher resistance materials
B) Using parallel connections
C) Using series connections
D) Increasing the circuit length
Answer: B) Using parallel connections

50. What does the slope of the V-I graph represent?
A) Power
B) Resistance
C) Current
D) Conductance
Answer: B) Resistance

51. Which is the best conductor of electricity?
A) Silver
B) Iron
C) Aluminum
D) Copper
Answer: A) Silver

52. What is the equivalent resistance of three 10 Ω resistors in parallel?

A)

3.33 Ω3.33 \, \Omega

B)

30 Ω30 \, \Omega

C)

10 Ω10 \, \Omega

D)

1 Ω1 \, \Omega

Answer: A)

3.33 Ω3.33 \, \Omega

53. What type of energy conversion occurs in an electric heater?
A) Electrical to light
B) Electrical to thermal
C) Electrical to mechanical
D) Electrical to chemical
Answer: B) Electrical to thermal

54. The heating element of an iron is made of:
A) Tungsten
B) Nichrome
C) Copper
D) Aluminum
Answer: B) Nichrome

55. Which of the following components of a circuit converts chemical energy to electrical energy?
A) Fuse
B) Bulb
C) Battery
D) Rheostat
Answer: C) Battery

56. In a series circuit, if one component fails, what happens?
A) All components fail
B) No change occurs
C) Voltage increases
D) Current increases
Answer: A) All components fail

57. What is the power consumed by a device operating at 220 V drawing 2 A of current?
A) 110 W
B) 440 W
C) 220 W
D) 660 W
Answer: B) 440 W

58. What happens to resistance when temperature increases in most conductors?
A) Increases
B) Decreases
C) Remains the same
D) Becomes zero
Answer: A) Increases

59. Which law states

V∝IV \propto I ?

A) Kirchhoff’s Law
B) Ohm’s Law
C) Faraday’s Law
D) Coulomb’s Law
Answer: B) Ohm’s Law

60. Which of the following is the unit of electric potential?
A) Joule
B) Ohm
C) Coulomb
D) Volt
Answer: D) Volt

61. If resistors are connected in parallel, the voltage across each resistor is:

A) The same
B) Different
C) Zero
D) Proportional to the resistance
Answer: A) The same

62. The SI unit of electric power is equivalent to:
A) Joule/second
B) Volt/ampere
C) Ohm/second
D) Coulomb/second
Answer: A) Joule/second

63. What happens to the resistance if the cross-sectional area of a wire is doubled?
A) Doubles
B) Halves
C) Remains the same
D) Becomes four times
Answer: B) Halves

64. How many joules are there in 1 kilowatt-hour?
A) 3.6×1063.6 \times 10^6
B) 3.6×1033.6 \times 10^3
C) 1.6×1061.6 \times 10^6
D) 6.3×1036.3 \times 10^3
Answer: A) 3.6×1063.6 \times 10^6

65. A device used to measure resistance is called a:
A) Rheostat
B) Ohmmeter
C) Voltmeter
D) Ammeter
Answer: B) Ohmmeter

66. If a wire of resistance $10\Omega$ is stretched to twice its original length, its resistance becomes:
A) 10 Ω10 \, \Omega
B) 20 Ω20 \, \Omega
C) 40 Ω40 \, \Omega
D) 5 Ω5 \, \Omega
Answer: C) 40 Ω40 \, \Omega

67. What is the commercial unit of electrical energy?
A) Joule
B) Watt-hour
C) Kilowatt-hour
D) Ampere-hour
Answer: C) Kilowatt-hour

68. The material with the lowest resistivity among the following is:
A) Copper
B) Iron
C) Tungsten
D) Nichrome
Answer: A) Copper

69. Which of the following represents the power dissipated in a resistor?
A) P=I2RP = I^2R
B) P=IRP = IR
C) P=I/RP = I/R
D) P=V/RP = V/R
Answer: A) P=I2RP = I^2R

70. What is the equivalent resistance when two 4 Ω4 \, \Omega resistors are connected in parallel?
A) 8 Ω8 \, \Omega
B) 4 Ω4 \, \Omega
C) 2 Ω2 \, \Omega
D) 1 Ω1 \, \Omega
Answer: C) 2 Ω2 \, \Omega

71. In a filament bulb, the filament is made of:
A) Copper
B) Iron
C) Tungsten
D) Aluminum
Answer: C) Tungsten

72. Which device protects circuits from excessive current?
A) Resistor
B) Voltmeter
C) Ammeter
D) Fuse
Answer: D) Fuse

73. The heating effect of current is used in:
A) Electric motor
B) Electric heater
C) Electric generator
D) Capacitor
Answer: B) Electric heater

74. If the potential difference across a conductor is 10 V and current through it is 2 A, the resistance is:
A) 5 Ω5 \, \Omega
B) 20 Ω20 \, \Omega
C) 10 Ω10 \, \Omega
D) 2 Ω2 \, \Omega
Answer: A) 5 Ω5 \, \Omega

75. What happens to the resistance of a conductor when the temperature decreases?
A) Increases
B) Decreases
C) Remains constant
D) Becomes zero
Answer: B) Decreases

76. The energy dissipated in a resistor is given by the formula:
A) E=VItE = VIt
B) E=I2RtE = I^2Rt
C) E=V2t/RE = V^2t/R
D) All of the above
Answer: D) All of the above

77. A conductor with a resistance of 2 Ω2 \, \Omega draws a current of 5 A5 \, \text{A}. What is the voltage across the conductor?
A) 5 V5 \, \text{V}
B) 10 V10 \, \text{V}
C) 15 V15 \, \text{V}
D) 20 V20 \, \text{V}
Answer: D) 20 V20 \, \text{V}

78. What is the resistance of a 220 V, 100 W bulb?
A) 220 Ω220 \, \Omega
B) 484 Ω484 \, \Omega
C) 110 Ω110 \, \Omega
D) 200 Ω200 \, \Omega
Answer: B) 484 Ω484 \, \Omega

79. Which metal is commonly used in overhead power lines due to its low density?
A) Copper
B) Aluminum
C) Silver
D) Tungsten
Answer: B) Aluminum

80. The resistivity of an insulator is typically in the range of:
A) 10−8 Ω m10^{-8} \, \Omega \, m
B) 10−6 Ω m10^{-6} \, \Omega \, m
C) 1010 Ω m10^{10} \, \Omega \, m
D) 10−3 Ω m10^{-3} \, \Omega \, m
Answer: C) 1010 Ω m10^{10} \, \Omega \, m

81. Which type of combination results in lower equivalent resistance?
A) Series
B) Parallel
C) Open circuit
D) Mixed
Answer: B) Parallel

82. A toaster uses 500 W500 \, \text{W} of power at 220 V220 \, \text{V}. What is its resistance?
A) 220 Ω220 \, \Omega
B) 110 Ω110 \, \Omega
C) 96.8 Ω96.8 \, \Omega
D) 45 Ω45 \, \Omega
Answer: C) 96.8 Ω96.8 \, \Omega

83. What is the current flowing through a 2 Ω2 \, \Omega resistor connected to a 6 V6 \, \text{V} battery?
A) 2 A2 \, \text{A}
B) 3 A3 \, \text{A}
C) 6 A6 \, \text{A}
D) 1 A1 \, \text{A}
Answer: B) 3 A3 \, \text{A}

84. Which of the following is the correct unit for resistance?
A) Ω\Omega
B) A/V
C) V/A
D) Both A and C
Answer: D) Both A and C

85. Which device stores electrical energy in a circuit?
A) Capacitor
B) Inductor
C) Resistor
D) Rheostat
Answer: A) Capacitor

86. The current through a 10 Ω10 \, \Omega resistor connected to a 100 V100 \, \text{V}source is:
A) 0.1 A0.1 \, \text{A}
B) 1 A1 \, \text{A}
C) 10 A10 \, \text{A}
D) 100 A100 \, \text{A}
Answer: B) 1 A1 \, \text{A}

87. In a series circuit, if one bulb is removed, the others:
A) Glow brighter
B) Stop glowing
C) Glow dimmer
D) Are unaffected
Answer: B) Stop glowing

88. What happens to total current in a parallel circuit when more branches are added?
A) Decreases
B) Increases
C) Remains the same
D) Becomes zero
Answer: B) Increases

89. A fuse is made of materials with:
A) High melting point
B) Low melting point
C) High resistivity
D) Low conductivity
Answer: B) Low melting point

90. The formula for calculating resistivity is:
A) R=ρl/AR = \rho l / A
B) ρ=RA/l\rho = RA/l
C) A=RρlA = R \rho l
D) None of these
Answer: B) ρ=RA/l\rho = RA/l

91. Which of the following materials is a good insulator?
A) Copper
B) Aluminum
C) Glass
D) Silver
Answer: C) Glass

92. What is the current through a 12 Ω12 \, \Omega resistor connected across a 24 V24 \, \text{V}source?
A) 0.5 A0.5 \, \text{A}
B) 1 A1 \, \text{A}
C) 2 A2 \, \text{A}
D) 12 A12 \, \text{A}
Answer: B) 2 A2 \, \text{A}

93. A bulb has a power rating of 60 W60 \, \text{W} at 240 V240 \, \text{V}. What is its resistance?
A) 240 Ω240 \, \Omega
B) 960 Ω960 \, \Omega
C) 480 Ω480 \, \Omega
D) 60 Ω60 \, \Omega
Answer: C) 960 Ω960 \, \Omega

94. What is the unit of conductance?
A) Ω−1\Omega^{-1}
B) Siemens
C) Both A and B
D) Farad
Answer: C) Both A and B

95. Which circuit component is used to vary resistance?
A) Resistor
B) Rheostat
C) Capacitor
D) Inductor
Answer: B) Rheostat

96. What is the resistance of an electric heater if it draws 10 A10 \, \text{A} from a 220 V220 \, \text{V} supply?
A) 2.2 Ω2.2 \, \Omega
B) 22 Ω22 \, \Omega
C) 220 Ω220 \, \Omega
D) 11 Ω11 \, \Omega
Answer: B) 22 Ω22 \, \Omega

97. A fuse protects circuits by:
A) Storing current
B) Absorbing voltage spikes
C) Melting when current is excessive
D) Regulating current
Answer: C) Melting when current is excessive

98. What is the SI unit of electric charge?
A) Volt
B) Ampere
C) Coulomb
D) Watt
Answer: C) Coulomb

99. If a 50 Ω50 \, \Omega resistor has a 5 A5 \, \text{A} current passing through it, the voltage across the resistor is:
A) 10 V10 \, \text{V}
B) 250 V250 \, \text{V}
C) 5 V5 \, \text{V}
D) 50 V50 \, \text{V}
Answer: B) 250 V250 \, \text{V}

100. In a parallel circuit, if one branch opens, the other branches:
A) Stop working
B) Work normally
C) Glow brighter
D) Work dimmer
Answer: B) Work normally