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Question
An electric bulb is rated 250 W, 230 V.
- the energy consumed in one hour, and
- the time in which the bulb will consume 1.0 kWh energy when connected to 230 V mains.
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Solution
(i) Given, Power (P) = 250 W, Voltage (V) = 230 V, Time (t) = 1 h = 3600 sec, Energy (E) = ?
Energy, E = P × t
Substituting the values in the formula above, we get,
E = 250 × 3600
E = 9 × 105 J
(ii) Let t be the time in which the bulb will consume 1.0 kWh energy when connected to 230 V mains.
P = 1.0 kWh = 1000 Wh
Substituting the value in the formula, we get,
⇒ 1000 = 250 × t
⇒ t = `1000/250`
⇒ t = 4 h
Hence, time = 4 h
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