Question

Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to an 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, the 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,
$Power=Voltage\times Current$
$Current=\frac{Power}{Voltage}=\frac{100}{220}A$
Current drawn by the bulb of rating 60 W is given by,
$Power=Voltage\times Current$
$Current=\frac{Power}{Voltage}=\frac{60}{220}A$
Hence, current drawn from the line =$\frac{100}{220}+\frac{60}{220}=0.727A$