Current Electricity

JEE Main level, single correct, medium

224 of 380

Question 224 of 380

An electric power line having total resistance of 2Ω2 \Omega, delivers 1 kW of power at 250 V. The percentage efficiency of transmission line is ____\_\_\_\_ .

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Answer: (C) 96.9

Current in transmission line: I=PV=1000250=4I = \frac{P}{V} = \frac{1000}{250} = 4 A.
Power loss: Ploss=I2R=42×2=32P_{loss} = I^2 R = 4^2 \times 2 = 32 W.
Efficiency: η=P−PlossP×100%\eta = \frac{P - P_{loss}}{P} \times 100\%
=1000−321000×100%= \frac{1000 - 32}{1000} \times 100\%
=96.8%= 96.8\% which rounds to 96.9%.

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