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Free Power MCQs with Answers

48 Power MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Power is the rate at which work is done or energy is transferred, with average power calculated over a time interval and instantaneous power found from P = Fv when force and velocity are aligned. Work includes units, mechanical efficiency, and the distinction between power and total work or energy.

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48 questions · page 3 of 3

41. 1KWh= _ J?

  • A. 3.6J
  • B. 3.6KJ
  • C. 3.6MJ
  • D. 3.6 GJ

Explanation: C is the correct option since 1 MJ = 10⁶ J, and we calculated 1 kWh = 3.6 × 10⁶ J = 3.6 MJ.

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Correct answer: 3.6MJ

42. An electric motor is used to lift the weight of 2.0N through a vertical distance of 100 cm in 4 sec. What is the power output of the motor?

  • A. 25 W
  • B. 0.5 W
  • C. 0.75 W
  • D. 1 W

Explanation: W=2.0N×1.0m=2.0JNext, the time taken to lift the weight is 4 seconds. Now we can find the power:P =work/time=2/4=0.5Watt

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Correct answer: 0.5 W

43. A lamp is connected to a 12-volt battery. An ammeter indicates a current of 5 mps. The watt of the lamp is:

  • A. 2.4 watts
  • B. 120 watts
  • C. 60 watts
  • D. 300 watts

Explanation: The question is asking for the watt or power of the lamp. We know that P = IV and we are given that I = 5 amps and V = 12 volts.

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Correct answer: 60 watts

44. If an amount of work △W is done by an agent in time interval △t, the power of that agency Will be:

  • A. △W /△t
  • B. △t / W△
  • C. △t / △W
  • D. △W + △t

Explanation: Thus power is defined as the rate of transfer of energy. In other words, we also define power.

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Correct answer: △W /△t

45. The dot product of force and velocity is equal to:

  • A. power
  • B. impulse
  • C. couple
  • D. Momentum

Explanation: Velocity=distance/time Force x velocity can also be written as force x distance or time force x distance = work done so the formula can be…

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Correct answer: power

46. An engine pumps out 40kg of water in second. The water comes out of vertically upward with a velocity of 3 ms-1, the power of engine in kilowatt is:

  • A. 1.2 kW
  • B. 12kW
  • C. 120kW
  • D. 1200kW

Explanation: Students should remember the formula of power i.e Force x speed So power = (mass x g) x speed assume g = 10] Power = (40 x 10) x 3 = 1200…

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Correct answer: 1.2 kW

47. Two boys weighting in the ratio 4:5 goes up stair taking time in the ratio 5:4. The ratio of their power is:

  • A. 1
  • B. 16/25
  • C. 25/16
  • D. 4/5

Explanation: Power of first boy / Power of second boy ∝ (Weight of first boy / Weight of second boy) × (Time taken by second boy / Time taken by first…

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Correct answer: 16/25

48. A 200N force acts on 8 kg crate that starts from rest. At the instant the object has gone 2m, the rate at which the force is doing work is:

  • A. 2.5 W
  • B. 25 W
  • C. 75 W
  • D. 2000 W

Explanation: To find the rate at which the force is doing work (power), we first need to determine the velocity of the crate after it has moved 2…

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Correct answer: 2000 W
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