Question

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

Answer 1

Both the bulbs are connected in parallel. Therefore, potential difference across each of them will be 220 V, because no division of voltage occurs in a parallel circuit.
Current drawn by the bulb of rating 100 W is given by,
Power = Voltage x Current
Current = $\frac {\text {Power}}{\text {Voltage}}$

Current = $\frac {60}{220} A$
Hence, current drawn from the line
$I$= $\frac {100}{220} +\frac {60}{220}$

$I$ = $\frac {160}{220}$

$I$= $\frac {8}{11}$

$I$ = $0.727 \ A$