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
\(I \)= \(\frac {100}{220} +\frac {60}{220}\)

\(I\) = \(\frac {160}{220}\)

\(I\)= \(\frac {8}{11}\)

\(I\) = \(0.727 \ A\)