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WAEC Physics 2015 Paper

Question : 36

Total: 50

\Omega

. Calculate the power loss in the cable.

Solution:

Concept:

Power loss in a cable is calculated using the formula

P_{\text{loss}} = I^2R

, where

I

is the current flowing through the cable and

R

is its resistance.

Explanation:

The generator is rated at

12\,\text{kW} = 12000\,\text{W}

and

2\,\text{kV} = 2000\,\text{V}

First, find the current using

P = IV

So,

I = \dfrac{P}{V} = \dfrac{12000}{2000} = 6\,\text{A}

The resistance of the cable is given as

R = 20\,\Omega

Now, calculate the power loss in the cable:

P_{\text{loss}} = I^2R = (6)^2 \times 20 = 36 \times 20 = 720\,\text{W}

Answer:

The power loss in the cable is

720\,\text{W}

, which is option C.

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