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Free Current Electricity MCQs with Answers

1,052 Current Electricity MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Steady current relates charge flow to potential difference, resistance and resistivity, including how temperature changes a conductor's resistance. Sources with internal resistance have terminal voltage below their emf when delivering current, and maximum power output occurs under a specific load condition rather than at zero resistance.

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Steady CurrentResistance and ResistivityTemperature Coefficient of ResistivityInternal Resistance of SourcesMaximum Power Output
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1,052 questions · page 11 of 53

201. A resistor of 5 Ω is connected in parallel with a series combination of 4 Ω and 6 Ω resistors. The equivalent resistance is:

  • A. 2 Ω
  • B. 3 Ω
  • C. 4 Ω
  • D. 5 Ω

Explanation: Series resistance = 4 + 6 = 10 Ω. Parallel combination: 1/Rₑ𝑞 = 1/5 + 1/10 = 2/10 + 1/10 = 3/10.

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Correct answer: 3 Ω

202. A circuit has three resistors of 2Ω each in parallel connected to a 12 V battery. The power dissipated by each resistor is:

  • A. 24 W
  • B. 48 W
  • C. 72W
  • D. 16 W

Explanation: Equivalent resistance for three 2 Ω resistors in parallel:1/Req = 1/2 + 1/2 + 1/2 = 3/2, so Req= 2/3 Ω.

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Correct answer: 72W

203. In a Kirchhoff's loop rule application, the equation for a loop is 18-4l1-6(l1 + l 2) = 0. If I₂ = 1 A, then I2 is:

  • A. 1A
  • B. 2A
  • C. 3A
  • D. 4A

Explanation: Simplify the loop equation: 18 - 4I₁ - 6I₁ - 6I₂ = 0. Substitute I₂ = 1 A: 18 - 10I₁ - 6 = 0, so 12 = 10I₁, and I₁ = 12/10 = 1.2 A…

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Correct answer: 1A

204. A wire has resistance 12 Ω. If it is bent into a circle and two points diametrically opposite are connected, the equivalent resistance between them is:

  • A. 3 Ω
  • B. 6 Ω
  • C. 9 Ω
  • D. 12 Ω

Explanation: The wire is divided into two semicircular paths, each with resistance 12/2 = 6 Ω.

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Correct answer: 3 Ω

205. A 60 W bulb is designed for 120 V. If connected to a 240 V supply, the power consumed is:

  • A. 60 W
  • B. 120 W
  • C. 240 W
  • D. 480 W

Explanation: Resistance R = V²/P = 120²/60 = 240 Ω. At 240 V, new power P' = V'²/R = 240²/240 = 240 W.

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Correct answer: 240 W

206. Two cells of emf 6 V and 4 V, each with internal resistance 1 Ω. are connected in series with an external resistor of 5 Ω. The current in the circuit is:

  • A. 0.5A
  • B. 1.5A
  • C. 3A
  • D. 2A

Explanation: Total emf = 6 + 4 = 10 V. Total resistance = 1 + 1 + 5 = 7 Ω. Current I = E/Rₜₒₜₐₗ = 10/7 ≈ 1.43 A, closest to 1.5 A.

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Correct answer: 1.5A

207. A potentiometer wire of length 1 m has a resistance of 10 Ω. A cell of emf 2 V is connected across it. The potential gradient along the wire is:

  • A. 0.2 V/m
  • B. 2 V/m
  • C. 0.02 V/m
  • D. 1 V/m

Explanation: Current I = V/R = 2/10 = 0.2 A. Potential drop across the wire = 2 V. Potential gradient = V/L = 2/1 = 2 V/m.

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Correct answer: 2 V/m

208. A circuit with a 10 V battery and resistors 2 Ω and 3 Ω in series is connected in parallel with a 5 Ω resistor. The total current from the battery is:

  • A. 2 A
  • B. 3 A
  • C. 4 A
  • D. 5 A

Explanation: Series branch resistance = 2 + 3 = 5 Ω. Parallel with 5 Ω: 1/Req = 1/5 + 1/5 = 2/5, so Req = 5/2 = 2.5 Ω.

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Correct answer: 4 A

209. A 100 Ω resistor and a 200 Ω resistor are connected in series with a 12 V battery. The potential difference across the 200 Ω resistor is:

  • A. 4V
  • B. 6V
  • C. 8V
  • D. 12V

Explanation: Total resistance = 100 + 200 = 300 Ω. Current I = V/R = 12/300 = 0.04 A. Voltage across 200 Ω = IR = 0.04 × 200 = 8 V.

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Correct answer: 8V

210. In a circuit, three resistors of 2 Ω, 3 Ω, and 6 Ω are connected in parallel across a 12 V battery with internal resistance 1 Ω. The current through the 3 Ω resistor is:

  • A. 2A
  • B. 3A
  • C. 4A
  • D. 5A

Explanation: Equivalent resistance of parallel resistors: 1/Rₚ = 1/2 + 1/3 + 1/6 = 3/6 + 2/6 + 1/6 = 1, so Rₚ = 1 Ω.

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Correct answer: 2A

211. A wire of resistance 16 Ω is cut into four equal parts, and two parts are connected in parallel. The equivalent resistance is:

  • A. 2Ω
  • B. 4Ω
  • C. 8Ω
  • D. 16Ω

Explanation: Each part has resistance 16/4 = 4 Ω. Two parts in parallel: 1/Req = 1/4 + 1/4 = 2/4, so Req= 4/2 = 2 Ω.

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Correct answer: 2Ω

212. A circuit has two batteries (E₁ = 10 V, r₁ = 1 Ω; E₂ = 5 V, r₂ = 2 Ω) in series with a 7 Ω resistor, with E₂ opposing E₁. The current in the circuit is:

  • A. 0.5 A
  • B. 1 A
  • C. 1.5 A
  • D. 2 A

Explanation: The net EMF is 10V-5V = 5V. Total resistance is 7Ω + 1Ω + 2Ω = 10Ω. Using Ohm's law, I = V/R = 5V/10Ω = 0.5A.

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Correct answer: 0.5 A

213. In a balanced Wheatstone bridge with resistors 5 Ω, 10 Ω, 8 Ω, and Rx, the unknown resistance Rx is:

  • A. 4Ω
  • B. 8Ω
  • C. 16Ω
  • D. 20Ω

Explanation: For a balanced Wheatstone bridge, R₁/R₂ = R₃/Rₓ. Using 5/10 = 8/Rₓ, we get Rₓ = 8 × 10/5 = 16 Ω.

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Correct answer: 16Ω

214. A potentiometer wire of length 2 m and resistance 20 Ω is connected to a 10 V battery. A cell of emf 2 V balances at 0.4 m. The emf of another cell balancing at 0.6 m is:

  • A. 2.5V
  • B. 3V
  • C. 4V
  • D. 5V

Explanation: Potential gradient = V/L = 10/2 = 5 V/m. For the first cell, emf = 5 × 0.4 = 2 V. For the second cell, emf = 5 × 0.6 = 3 V.

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Correct answer: 3V

215. A circuit has three resistors: 4 Ω and 8 Ω in parallel, connected in series with a 6 Ω resistor and a 12 V battery. The power dissipated in the 6 Ω resistor is:

  • A. 6W
  • B. 8W
  • C. 12W
  • D. 18W

Explanation: Parallel resistance: 1/Rₚ = 1/4 + 1/8 = 3/8, so Rₚ = 8/3 Ω. Total resistance = 8/3 + 6 = 26/3 Ω. Current I = 12/(26/3) = 18/13 A.

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Correct answer: 12W

216. Two cells (E₁ = 6 V, r₁ = 1 Ω; E₂ = 4 V, r₂ = 1 Ω) are connected in parallel to a 5 Ω resistor. The equivalent emf of the combination is:

  • A. 5 V
  • B. 4V
  • C. 6V
  • D. 4.5 V

Explanation: For parallel cells, equivalent emf Eₑ𝑞 = (E₁/r₁ + E₂/r₂)/(1/r₁ + 1/r₂) = (6/1 + 4/1)/(1/1 + 1/1) = 10/2 = 5 V.

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Correct answer: 5 V

217. A 100 Ω resistor is connected to a 220 V supply. If a second identical resistor is added in series, the total power consumed is:

  • A. 242 W
  • B. 121 W
  • C. 484 W
  • D. 60.5 W

Explanation: Single resistor power = V²/R = 220²/100 = 484 W. In series, Rtotal = 100 + 100 = 200 Ω.

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Correct answer: 121 W

218. A circuit with a 10 V battery and three resistors (2 Ω, 3 Ω, 5 Ω) in series is shunted by a 4 Ω resistor across the 3 Ω resistor. The current through the 4 Ω resistor is:

  • A. 0.5 A
  • B. 1 A
  • C. 1.5 A
  • D. 2 A

Explanation: Series resistance without shunt = 2 + 3 + 5 = 10 Ω. With 4 Ω shunting 3 Ω, the equivalent resistance of parallel = (3 × 4)/(3 + 4) = 12/7…

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Correct answer: 0.5 A

219. A wire of resistance R is bent into a square, and a battery is connected across one side. The equivalent resistance across adjacent corners is:

  • A. 3R/16
  • B. R/4
  • C. R/2
  • D. 3R/4

Explanation: The total resistance (R) of the wire is split into two parallel paths across adjacent corners: a short path of R/4 and a long path of…

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Correct answer: 3R/16

220. A circuit consists of a 15 V battery with internal resistance 2 Ω connected to two parallel branches: one with 4 Ω and 6 Ω in series, and the other with 8 Ω. The total current supplied by the battery is:

  • A. 1 A
  • B. 2 A
  • C. 3 A
  • D. 4 A

Explanation: Series branch resistance = 4 + 6 = 10 Ω. Parallel with 8 Ω: 1/Rₑ𝑞 = 1/10 + 1/8 = 4/40 + 5/40 = 9/40, so Rₑ𝑞 = 40/9 Ω.

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Correct answer: 2 A
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