NEET 2026, Physics Q2: Energy, Power And Heating Effect

NEET2026Physics

A room heater is rated 400 W, 220V. If the supply voltage drops to 200 V, what will be the power consumed (approximately) ?

Solution

The resistance of the heater is fixed by its rating:

$R_{H} = \frac{V ^{2}}{P} = \frac{( 220 ) ^{2}}{400}$

At a supply voltage $V_{s} = 200$ V, the actual power consumed is

$P^{'} = \frac{V _{s}^{2}}{R _{H}} = \frac{( 200 ) ^{2}}{( 220 ) ^{2}} \times 400 \approx 330.6 W \approx 331 W$

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