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RRB Physics (Electricity) – 100 MCQs

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RRB Physics (Electricity) – 100 MCQs

 Electricity MCQs (1–50) – 

1) SI unit of electric current is:

A) Volt
B) Ampere
C) Ohm
D) Watt
✅ Show Answer
Answer: B) Ampere
Explanation: Electric current is measured in Ampere (A).

2) Unit of electric charge is:
A) Coulomb
B) Ampere
C) Watt
D) Volt
✅ Show Answer
Answer: A) Coulomb
Explanation: Electric charge is measured in Coulomb (C).

3) The instrument used to measure potential difference is:
A) Ammeter
B) Voltmeter
C) Galvanometer
D) Thermometer
✅ Show Answer
Answer: B) Voltmeter
Explanation: Voltmeter measures potential difference across two points.

4) SI unit of potential difference is:
A) Volt
B) Ampere
C) Ohm
D) Joule
✅ Show Answer
Answer: A) Volt
Explanation: Potential difference is measured in Volt (V).

5) Ohm’s Law is represented by:
A) V = IR
B) P = VI
C) F = ma
D) W = Fs
✅ Show Answer
Answer: A) V = IR
Explanation: According to Ohm’s law, voltage equals current × resistance.

6) Resistance is measured in:
A) Volt
B) Ohm
C) Ampere
D) Coulomb
✅ Show Answer
Answer: B) Ohm
Explanation: Unit of resistance is Ohm (Ω).

7) Resistance of a conductor depends on:
A) Length of conductor
B) Area of cross-section
C) Material of conductor
D) All of these
✅ Show Answer
Answer: D) All of these
Explanation: R = ρL/A depends on material, length and area.

8) Resistance increases when:
A) Length increases
B) Area increases
C) Length decreases
D) Temperature decreases
✅ Show Answer
Answer: A) Length increases
Explanation: Resistance is directly proportional to length.

9) Resistance decreases when:
A) Length increases
B) Area decreases
C) Area increases
D) Temperature increases
✅ Show Answer
Answer: C) Area increases
Explanation: Resistance is inversely proportional to area (R ∝ 1/A).

10) Ohm’s law is valid only when:
A) Pressure is constant
B) Temperature is constant
C) Volume is constant
D) Current is constant
✅ Show Answer
Answer: B) Temperature is constant
Explanation: Ohm’s law holds for constant physical conditions like temperature.

11) A wire offers more resistance if it is:
A) Short and thick
B) Long and thin
C) Short and thin
D) Long and thick
✅ Show Answer
Answer: B) Long and thin
Explanation: Resistance increases with length and decreases with area.

12) A material used for bulb filament is:
A) Copper
B) Tungsten
C) Aluminium
D) Silver
✅ Show Answer
Answer: B) Tungsten
Explanation: Tungsten has high melting point so it can glow without melting.

13) Fuse wire should have:
A) High melting point
B) Low melting point
C) No melting point
D) Very high conductivity always
✅ Show Answer
Answer: B) Low melting point
Explanation: Fuse melts quickly during overload to protect appliances.

14) The fuse is always connected in:
A) Parallel
B) Series
C) Both
D) None
✅ Show Answer
Answer: B) Series
Explanation: It must break the whole circuit when current is high.

15) Electrical energy is commercially measured in:
A) Joule
B) Watt
C) kWh
D) Ampere
✅ Show Answer
Answer: C) kWh
Explanation: Electricity bill uses kilowatt hour (unit).

16) 1 kWh equals:
A) 3.6 × 10⁵ J
B) 3.6 × 10⁶ J
C) 3.6 × 10⁷ J
D) 36 × 10⁶ J
✅ Show Answer
Answer: B) 3.6 × 10⁶ J
Explanation: 1 unit = 1000W × 3600s = 3.6×10⁶J.

17) The rate of flow of charge is called:
A) Voltage
B) Resistance
C) Current
D) Power
✅ Show Answer
Answer: C) Current
Explanation: Current = charge/time.

18) Conventional current flows from:
A) Negative to positive
B) Positive to negative
C) Both directions
D) No direction
✅ Show Answer
Answer: B) Positive to negative
Explanation: Conventional direction is opposite to electron flow.

19) The device used to control current is:
A) Voltmeter
B) Rheostat
C) Ammeter
D) Fuse
✅ Show Answer
Answer: B) Rheostat
Explanation: Rheostat is a variable resistance used to adjust current.

20) In a series circuit, current is:
A) Same in all components
B) Different in all components
C) Zero
D) Infinite
✅ Show Answer
Answer: A) Same in all components
Explanation: In series, same current flows through every resistor.

21) In parallel circuit, voltage is:
A) Same across each branch
B) Different across each branch
C) Zero
D) Infinite
✅ Show Answer
Answer: A) Same across each branch
Explanation: Each branch gets same potential difference.

22) Total resistance in series is:
A) Difference of resistances
B) Sum of resistances
C) Product of resistances
D) Zero
✅ Show Answer
Answer: B) Sum of resistances
Explanation: Series: R = R1 + R2 + R3…

23) Total resistance in parallel is always:
A) Greater than highest resistance
B) Less than smallest resistance
C) Equal to sum of resistances
D) Infinite
✅ Show Answer
Answer: B) Less than smallest resistance
Explanation: Parallel connection decreases effective resistance.

24) The heating effect of current is given by:
A) H = IRT
B) H = I²Rt
C) H = IR²t
D) H = VIt²
✅ Show Answer
Answer: B) H = I²Rt
Explanation: Joule’s law: Heat produced depends on square of current.

25) Electric power is given by:
A) P = VI
B) P = IR
C) P = V/R
D) P = I/R
✅ Show Answer
Answer: A) P = VI
Explanation: Power = Voltage × Current.

26) The unit of electric power is:
A) Joule
B) Watt
C) Volt
D) Ampere
✅ Show Answer
Answer: B) Watt
Explanation: Electric power is measured in watts (W).

27) If current is doubled, heat produced becomes:
A) Double
B) Four times
C) Half
D) One-fourth
✅ Show Answer
Answer: B) Four times
Explanation: Heat ∝ I². Doubling I → 4 times heat.

28) Current is measured by:
A) Voltmeter
B) Ammeter
C) Thermometer
D) Barometer
✅ Show Answer
Answer: B) Ammeter
Explanation: Ammeter measures current in amperes.

29) Voltmeter is connected in:
A) Series
B) Parallel
C) Both
D) None
✅ Show Answer
Answer: B) Parallel
Explanation: Voltmeter is connected parallel to measure potential difference.

30) Ammeter is connected in:
A) Parallel
B) Series
C) Both
D) None
✅ Show Answer
Answer: B) Series
Explanation: Ammeter must be in series to measure same current flow.

31) An ideal voltmeter has resistance:
A) Zero
B) Very high
C) Very low
D) Equal to wire
✅ Show Answer
Answer: B) Very high
Explanation: High resistance ensures minimum current is drawn by voltmeter.

32) An ideal ammeter has resistance:
A) Very high
B) Very low
C) Infinite
D) Depends on voltage
✅ Show Answer
Answer: B) Very low
Explanation: Low resistance allows current without drop in circuit.

33) The resistance of a metal wire increases with:
A) Decrease in temperature
B) Increase in temperature
C) Decrease in length
D) Increase in area
✅ Show Answer
Answer: B) Increase in temperature
Explanation: For metals, resistance increases with temperature.

34) If R increases, current (I) will:
A) Increase
B) Decrease
C) Remain same
D) Become infinite
✅ Show Answer
Answer: B) Decrease
Explanation: I = V/R, so higher resistance means lower current.

35) If V increases, current (I) will:
A) Decrease
B) Increase
C) Become zero
D) Remain same always
✅ Show Answer
Answer: B) Increase
Explanation: I ∝ V if resistance constant.

36) A short circuit occurs when:
A) High resistance path is formed
B) Very low resistance path is formed
C) Current becomes zero
D) Voltage becomes zero always
✅ Show Answer
Answer: B) Very low resistance path is formed
Explanation: Live and neutral touch → high current flows due to low resistance.

37) Overloading is due to:
A) Low current
B) High current
C) Low voltage
D) Low resistance always
✅ Show Answer
Answer: B) High current
Explanation: Using many appliances draws more current than safe limit.

38) Household electrical appliances are connected in:
A) Series
B) Parallel
C) Both series and parallel
D) No connection
✅ Show Answer
Answer: B) Parallel
Explanation: Parallel ensures same voltage and independent working.

39) The earth wire is used for:
A) Increasing current
B) Safety from electric shock
C) Increasing voltage
D) Saving power
✅ Show Answer
Answer: B) Safety from electric shock
Explanation: Earth wire provides low resistance path to ground.

40) Colour of earth wire is generally:
A) Red
B) Blue
C) Green
D) White
✅ Show Answer
Answer: C) Green
Explanation: Earth wire is green (or green-yellow).

41) The live wire is generally of colour:
A) Green
B) Red/Brown
C) Blue
D) Yellow only
✅ Show Answer
Answer: B) Red/Brown
Explanation: Live wire is usually red (old) or brown (new coding).

42) The neutral wire is generally of colour:
A) Blue/Black
B) Green
C) Red
D) White only
✅ Show Answer
Answer: A) Blue/Black
Explanation: Neutral wire is generally blue (new) or black (old).

43) Main switch is always connected to:
A) Neutral wire only
B) Live wire only
C) Earth wire only
D) Neutral and earth wires
✅ Show Answer
Answer: B) Live wire only
Explanation: For safety, switch should cut off live supply.

44) A battery supplies:
A) Alternating current (AC)
B) Direct current (DC)
C) Both AC & DC
D) No current
✅ Show Answer
Answer: B) Direct current (DC)
Explanation: Battery produces DC.

45) AC changes its direction:
A) Never
B) Only once
C) Periodically
D) Randomly
✅ Show Answer
Answer: C) Periodically
Explanation: AC reverses direction again and again.

46) Frequency of AC in India is:
A) 60 Hz
B) 50 Hz
C) 25 Hz
D) 100 Hz
✅ Show Answer
Answer: B) 50 Hz
Explanation: India has 50 cycles per second AC frequency.

47) Electric power formula is:
A) P = VI
B) P = IR
C) P = V/R
D) P = I/R
✅ Show Answer
Answer: A) P = VI
Explanation: Electric power = Voltage × Current.

48) A device that converts electrical energy into heat is:
A) Generator
B) Heater
C) Motor
D) Transformer
✅ Show Answer
Answer: B) Heater
Explanation: Heater works on heating effect of current.

49) The filament in bulb glows due to:
A) Chemical effect
B) Heating effect
C) Magnetic effect
D) Electrolysis
✅ Show Answer
Answer: B) Heating effect
Explanation: Filament becomes hot and glows.

50) The direction of electron flow is:
A) Positive to negative
B) Negative to positive
C) Both directions
D) Random direction
✅ Show Answer
Answer: B) Negative to positive
Explanation: Electrons flow from negative terminal to positive terminal.

51) Electric current is defined as:
A) Flow of neutrons
B) Rate of flow of charge
C) Rate of flow of energy
D) Flow of atoms
✅ Show Answer
Answer: B) Rate of flow of charge
Explanation: Current = charge flowing per unit time.

52) Which of the following is a good conductor of electricity?
A) Rubber
B) Plastic
C) Copper
D) Glass
✅ Show Answer
Answer: C) Copper
Explanation: Copper has low resistivity and allows current to flow easily.

53) The resistance of a conductor is directly proportional to:
A) Its length
B) Its area
C) Its volume
D) Its density
✅ Show Answer
Answer: A) Its length
Explanation: R ∝ L (resistance increases with length).

54) The resistance of a conductor is inversely proportional to:
A) Length
B) Area of cross-section
C) Temperature
D) Resistivity
✅ Show Answer
Answer: B) Area of cross-section
Explanation: R ∝ 1/A, larger area means lower resistance.

55) The SI unit of electric power is:
A) Joule
B) Watt
C) Volt
D) Coulomb
✅ Show Answer
Answer: B) Watt
Explanation: Power is measured in Watt (W).

56) The electric power of a device can be calculated by:
A) P = VI
B) P = V/I
C) P = IR
D) P = R/I
✅ Show Answer
Answer: A) P = VI
Explanation: Electric power is voltage multiplied by current.

57) The unit of electrical energy used in homes is:
A) Joule
B) kWh
C) Watt
D) Ampere
✅ Show Answer
Answer: B) kWh
Explanation: Household energy is measured in kilowatt-hour (unit).

58) 1 kilowatt =
A) 100 W
B) 1000 W
C) 10,000 W
D) 1 W
✅ Show Answer
Answer: B) 1000 W
Explanation: 1 kW = 1000 watts.

59) The heating effect of current is used in:
A) Electric iron
B) Electric heater
C) Electric toaster
D) All of these
✅ Show Answer
Answer: D) All of these
Explanation: All devices use heat produced by electric current.

60) A short circuit leads to:
A) Very low current
B) Very high current
C) Zero voltage
D) Very high resistance
✅ Show Answer
Answer: B) Very high current
Explanation: Low resistance path → huge current flows.

61) Overloading happens when:
A) Many appliances are connected to one socket
B) Voltage is low
C) Resistance increases
D) Current becomes zero
✅ Show Answer
Answer: A) Many appliances are connected to one socket
Explanation: More load draws more current than safe limit.

62) The best conductor among these is:
A) Silver
B) Plastic
C) Rubber
D) Wood
✅ Show Answer
Answer: A) Silver
Explanation: Silver has very low resistivity, excellent conductor.

63) The relation between resistivity (ρ), resistance (R), length (L), area (A) is:
A) R = ρA/L
B) R = ρL/A
C) R = ρLA
D) R = ρ/L²
✅ Show Answer
Answer: B) R = ρL/A
Explanation: Resistance formula: R = ρL/A.

64) If length of wire is halved, resistance becomes:
A) Double
B) Half
C) Four times
D) Same
✅ Show Answer
Answer: B) Half
Explanation: Resistance is proportional to length (R ∝ L).

65) If area of wire is doubled, resistance becomes:
A) Double
B) Half
C) Four times
D) Same
✅ Show Answer
Answer: B) Half
Explanation: Resistance is inversely proportional to area (R ∝ 1/A).

66) In series connection, voltage divides across resistors because:
A) Current is different
B) Current is same but resistance differs
C) Resistance is zero
D) Voltage is zero
✅ Show Answer
Answer: B) Current is same but resistance differs
Explanation: V = IR, so different R gives different voltage drop.

67) In parallel connection, current divides because:
A) Voltage is different
B) Voltage is same but resistance differs
C) Resistance is infinite
D) Current is constant
✅ Show Answer
Answer: B) Voltage is same but resistance differs
Explanation: I = V/R, lower R branch carries more current.

68) The SI unit of resistivity is:
A) Ωm
B) Ω/m
C) m/Ω
D) Ωm²
✅ Show Answer
Answer: A) Ωm
Explanation: Resistivity unit is Ohm metre (Ωm).

69) Copper is used for wiring because:
A) It has very high resistance
B) It has low resistivity
C) It has no conductivity
D) It produces more heat
✅ Show Answer
Answer: B) It has low resistivity
Explanation: Low resistivity means better conductor and less power loss.

70) The effect of electric current used in electroplating is:
A) Heating effect
B) Chemical effect
C) Magnetic effect
D) None
✅ Show Answer
Answer: B) Chemical effect
Explanation: Electroplating is done using chemical effect of electric current.

71) The instrument used to detect small current is:
A) Voltmeter
B) Ammeter
C) Galvanometer
D) Rheostat
✅ Show Answer
Answer: C) Galvanometer
Explanation: Galvanometer is very sensitive and detects small currents.

72) If 2Ω and 3Ω resistors are connected in series, total resistance is:
A) 1Ω
B) 5Ω
C) 6Ω
D) 0.5Ω
✅ Show Answer
Answer: B) 5Ω
Explanation: Series resistance adds: 2 + 3 = 5Ω.

73) If 2Ω and 3Ω resistors are connected in parallel, effective resistance is:
A) 5Ω
B) 1.2Ω
C) 6Ω
D) 0.6Ω
✅ Show Answer
Answer: B) 1.2Ω
Explanation: 1/R = 1/2 + 1/3 = 5/6 ⇒ R = 6/5 = 1.2Ω.

74) A fuse protects an electric circuit by:
A) Increasing the current
B) Breaking the circuit when current is excessive
C) Increasing voltage
D) Decreasing resistance
✅ Show Answer
Answer: B) Breaking the circuit when current is excessive
Explanation: Fuse melts due to heat and opens the circuit.

75) Electric current produces heat due to:
A) Low resistance
B) High resistance
C) No resistance
D) Voltage only
✅ Show Answer
Answer: B) High resistance
Explanation: Heat is produced when current flows through resistance.

76) A resistor of 10Ω carries current 2A. Voltage across it is:
A) 5V
B) 10V
C) 20V
D) 40V
✅ Show Answer
Answer: C) 20V
Explanation: V = IR = 2×10 = 20V.

77) Which of the following is an insulator?
A) Copper
B) Aluminium
C) Rubber
D) Iron
✅ Show Answer
Answer: C) Rubber
Explanation: Rubber does not allow electric current to pass easily.

78) The unit of electric current is:
A) Watt
B) Ampere
C) Volt
D) Ohm
✅ Show Answer
Answer: B) Ampere
Explanation: Current is measured in Ampere (A).

79) The unit of resistance is:
A) Watt
B) Volt
C) Ohm
D) Joule
✅ Show Answer
Answer: C) Ohm
Explanation: Resistance is measured in ohm (Ω).

80) The unit of voltage is:
A) Ampere
B) Volt
C) Ohm
D) Watt
✅ Show Answer
Answer: B) Volt
Explanation: Voltage (potential difference) is measured in volts.

81) The unit of electric charge is:
A) Coulomb
B) Ampere
C) Joule
D) Watt
✅ Show Answer
Answer: A) Coulomb
Explanation: Charge is measured in Coulomb (C).

82) Resistance of a wire depends on:
A) Length
B) Area
C) Material
D) All of these
✅ Show Answer
Answer: D) All of these
Explanation: R depends on L, A and material resistivity.

83) Resistance decreases when:
A) Length increases
B) Area increases
C) Temperature increases
D) Length increases and area decreases
✅ Show Answer
Answer: B) Area increases
Explanation: Larger cross-sectional area reduces resistance.

84) The power consumed in a circuit is:
A) P = VI
B) P = V/I
C) P = IR
D) P = R/I
✅ Show Answer
Answer: A) P = VI
Explanation: Power = Voltage × Current.

85) The material used for fuse wire is:
A) Tungsten
B) Alloy with low melting point
C) Copper
D) Iron
✅ Show Answer
Answer: B) Alloy with low melting point
Explanation: Fuse wire is made of alloy (tin-lead) which melts quickly.

86) The main purpose of earth wire is to:
A) Reduce voltage
B) Prevent electric shock
C) Increase current
D) Increase resistance
✅ Show Answer
Answer: B) Prevent electric shock
Explanation: Earth wire provides safe path for leakage current.

87) Which connection is used in home wiring?
A) Series connection
B) Parallel connection
C) Both series and parallel together
D) No connection
✅ Show Answer
Answer: B) Parallel connection
Explanation: Parallel ensures equal voltage and independent control.

88) If current is doubled, power (P = I²R) becomes:
A) Double
B) Four times
C) Half
D) Same
✅ Show Answer
Answer: B) Four times
Explanation: Power depends on square of current in I²R formula.

89) The resistance of an ideal ammeter is:
A) Very high
B) Very low
C) Infinite
D) Variable
✅ Show Answer
Answer: B) Very low
Explanation: Ammeter must not change circuit current.

90) The resistance of an ideal voltmeter is:
A) Very low
B) Very high
C) Zero
D) Infinite current
✅ Show Answer
Answer: B) Very high
Explanation: Voltmeter should draw minimum current.

91) Which statement is correct?
A) Ammeter is connected in parallel
B) Voltmeter is connected in series
C) Ammeter is connected in series
D) Voltmeter is connected to earth wire
✅ Show Answer
Answer: C) Ammeter is connected in series
Explanation: Ammeter must measure current passing through circuit.

92) The phenomenon of depositing metal using electric current is:
A) Heating
B) Electroplating
C) Reflection
D) Induction
✅ Show Answer
Answer: B) Electroplating
Explanation: Metal deposition is done using chemical effect of current.

93) Electric power can also be written as:
A) P = I²R
B) P = IR²
C) P = V²I
D) P = R²/I
✅ Show Answer
Answer: A) P = I²R
Explanation: Derived using P=VI and V=IR.

94) If the resistance of a circuit is 5Ω and voltage is 10V, current is:
A) 1A
B) 2A
C) 5A
D) 10A
✅ Show Answer
Answer: B) 2A
Explanation: I = V/R = 10/5 = 2A.

95) A 60W bulb used for 2 hours consumes energy:
A) 0.06 kWh
B) 0.12 kWh
C) 1.2 kWh
D) 12 kWh
✅ Show Answer
Answer: B) 0.12 kWh
Explanation: Energy = 0.06 kW × 2h = 0.12 kWh.

96) A device that gives reading in kWh is:
A) Voltmeter
B) Ammeter
C) Energy meter
D) Galvanometer
✅ Show Answer
Answer: C) Energy meter
Explanation: Energy meter measures electrical energy used (units).

97) The flow of electrons in a conductor produces:
A) Electric current
B) Electric pressure
C) Electric heat only
D) No effect
✅ Show Answer
Answer: A) Electric current
Explanation: Movement of electrons in conductor is current.

98) The function of a switch is to:
A) Increase current
B) Break or complete circuit
C) Measure voltage
D) Store charge
✅ Show Answer
Answer: B) Break or complete circuit
Explanation: Switch turns circuit ON/OFF by opening or closing path.

99) Electric current is a:
A) Vector quantity
B) Scalar quantity
C) Both scalar and vector
D) None
✅ Show Answer
Answer: B) Scalar quantity
Explanation: Current has magnitude only, direction is conventional.

100) Electric bulb converts electrical energy into:
A) Heat only
B) Light only
C) Both heat and light
D) Mechanical energy
✅ Show Answer
Answer: C) Both heat and light
Explanation: Bulb produces light and also releases heat.
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