Question

An engine uses 30 A of current. The resistance offered is 15 ohms. Calculate the power consumed by the engine in horse power.

(a) 18 hp

(b) 19 hp

(c) 17 hp

(d) 13500 hp

This question was posed to me in an international level competition.

Origin of the question is Current Electricity topic in portion Current Electricity of Physics – Class 12

Answer 1

The correct choice is (a) 18 hp

Easiest explanation: Current used = 30 A; Resistance = 15 ohms

The required equation is: Power = current^2 × resistance

= 30 × 30 × 15

  = 13,500 Watts

  We know that, 1 Watt = 746 horse power (hp). So, 13,500 Watts = 18.096 hp, which can approximately be equal to 18 hp.

Therefore, the engine consumes 18 hp power.