Two lamps, one rated 100 W at 220 V

Two lamps, one rated $100 \mathrm{~W}$ at $220 \mathrm{~V}$, and the other $60 \mathrm{~W}$ at $220 \mathrm{~V}$, are connected in parallel to the electric mains supply. What current is drawn from the line if the supply voltage is 220 V ?

Resistance of first lamp,


resistance of the second lamp,


Since the two lamps are connected in parallel, the equivalent resistance is given by


or $\mathrm{R}_{\mathrm{P}}=\frac{(220)^{2}}{160}=\mathbf{3 0 2 . 5} \boldsymbol{\Omega}$

Current drawn from the line, i.e.,

$I=\frac{V}{R_{p}}=\frac{220 V}{302.5 \Omega}=0.727 \mathrm{~A}$

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