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Question
A light bulb is rated 100 W for 220 V ac supply of 50 Hz. Calculate
(i) The resistance of the bulb;
(ii) The rms current through the bulb.
Solution
P = 100 W Vrms = 220 V
(a) Resistance, R
`=V_(rms)^2/P = (220 xx 220)/100 Ω =484Omega`
(b) P = Irms Vrms
`I_(rmo) =P/V_(rms) = (100W)/(220V)` = 0.45A
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