JEE Main 2026 — Jan 22, Shift 2 — Physics solution

JEE Main2026Jan 22, Shift 2Physics

An electric power line having total resistance of 2 Ω, delivers 1 kW of power of 250 V. The percentage efficiency of transmission line is _____.

Solution

Delivered power $P_{o u t} = 1000$ W at $V = 250$ V, so current $I = \frac{1000}{250} = 4$ A.

Power loss in the line: $P_{l oss} = I^{2} R = 16 \times 2 = 32$ W.

Input (net) power $P_{n e t} = P_{o u t} + P_{l oss} = 1032$ W.

Efficiency $η = \frac{P _{o u t}}{P _{n e t}} \times 100 = \frac{1000}{1032} \times 100 \approx 96.9%$ .

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