Current Electricity and Electrical InstrumentHard

Question

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

Options

A.96.9
B.86.5
C.100
D.92.5

Solution

$P_{\text{out~}} = 1000\text{ }W$

$${P = VI }{1000 = 250 \times I }{I = 4\text{ }A }{P_{\text{loss~}} = I^{2}R = (4)^{2} \times 2 = 3200 }{P_{\text{net~}} = 1000 + 32 = 103200 }{\eta = \left( \frac{P_{\text{out~}}}{P_{\text{net~}}} \right) \times 100 = \frac{1000}{1032} \times 100 = 96.9\%}$$

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