The resistance of a 100 W, 200 V lamp is

Question

Examoogle · Accepted Answer

400 $\Omega$

Explanation: Given: Power P = 100 W, Voltage V = 200 V

Formula Used: $$R = \frac{V^2}{P}$$

Steps: Identify the given parameters: From the problem statement, we have the power rating $P = 100	ext{ W}$ and the voltage rating $V = 200	ext{ V}$.. Select the appropriate formula: The relationship between power, voltage, and resistance is given by the formula $P = \frac{V^2}{R}$. Rearranging this for resistance $R$, we get $R = \frac{V^2}{P}$.. Substitute and Calculate: Substitute the given values into the formula: $R = \frac{200^2}{100} = \frac{40000}{100}$.

Answer: C is correct because the resistance $R$ calculated using the formula $R = V^2/P$ results in $400\, \Omega$.

Exam Tip: Always verify if a device is operating at its rated voltage; if it is, the resistance remains constant and can be calculated directly from the nameplate ratings.

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