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An electric kettle takes 4A current at 220V. How much time will it take to boil 1 kg of water from temperature 20°C? The temperature of boiling water is 100°C.

1. 6.3 min
2. 8.4 min
3. 12.6 min
4. 4.2 min

Correct answer: 8.4 min

Solution

The power of the kettle is calculated using P = VI = 220 × 4 = 880 W. The heat required to boil water is Q = mcΔT = 1 × 4200 × (100 - 20) = 336000 J. Time is given by t = Q/P = 336000/880 = 381.8 seconds ≈ 6.3 minutes.

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