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WAEC Physics 2019 Paper

Question : 32

Total: 49

Solution:

Concept:

The electric power consumed by a resistor is related to the voltage across it and its resistance by

P = \frac{V^2}{R}

Explanation:

Given power,

P = 100\ \mathrm{W}

and voltage,

V = 120\ \mathrm{V}

Rearrange the power formula to make resistance the subject:

R = \frac{V^2}{P}

Substitute the given values into the formula:

R = \frac{(120\ \mathrm{V})^2}{100\ \mathrm{W}}

Simplify the numerator:

(120)^2 = 14400

So,

R = \frac{14400}{100} = 144\ \Omega

Answer:

144\ \Omega

Correct option: D.

144\ \Omega

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