NEET · Physics · STD 12 - 3. current electricity
A room heater is rated 400 W, 220 V. If the supply voltage drops to 200 V, what will be the power consumed (approximately) ?
- A 200 W
- B 400 W
- C 331 W
- D 121 W
Answer & Solution
Correct Answer
(C) 331 W
Step-by-step Solution
Detailed explanation
(C) 331 W
The resistance of the room heater is given by \(R=\frac{V^2}{P}\)
Substituting the rated values, \(R=\frac{220^2}{400}=\frac{48400}{400}=121 \Omega\)
When the supply voltage drops to \(V^{\prime}=200 V\), the power consumed is \(P^{\prime}=\frac{V^{\prime 2}}{R}\)
\(P^{\prime}=\frac{200^2}{121}=\frac{40000}{121} \approx 330.57 W\)
Therefore, the power consumed is approximately \(3 3 1 ~ W\).
The resistance of the room heater is given by \(R=\frac{V^2}{P}\)
Substituting the rated values, \(R=\frac{220^2}{400}=\frac{48400}{400}=121 \Omega\)
When the supply voltage drops to \(V^{\prime}=200 V\), the power consumed is \(P^{\prime}=\frac{V^{\prime 2}}{R}\)
\(P^{\prime}=\frac{200^2}{121}=\frac{40000}{121} \approx 330.57 W\)
Therefore, the power consumed is approximately \(3 3 1 ~ W\).
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