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An electric tungsten bulb is connected into a home circuit. The home electric supply runs at 220 V potential difference. When switch on, a current of 0.45 A flows through the bulb :(a) What must be power (wattage) of the bulb ?(b) If it is kept on fo…

Q.3 (ii) An electric tungsten bulb is connected into a home circuit. The home electric supply runs at 220 V potential difference. When switch on, a current of 0.45 A flows through the bulb :
(a) What must be power (wattage) of the bulb ?
(b) If it is kept on for 10 hours, how many units of electricity will be consumed ?

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Answer: (a) 99 W; (b) about 1 unit (0.99 kWh).

(a) \(P = VI = 220 \times 0.45 = 99\) W, so the bulb is of about 100 W.

(b) Energy = power × time = \(99\ \text{W} \times 10\ \text{h} = 990\ \text{Wh} = 0.99\ \text{kWh}\).

1 unit of electricity = 1 kWh, so the bulb consumes about 1 unit (0.99 unit) in 10 hours.

Doubtly AI · 25 Oct 2026 AI-verified · Oct 2026 Report
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