Question

Two $220$ volt, $100$ watt bulbs are connected first in series and then in parallel. Each time the combination is connected to a $220$ volt a.c. supply line. The power drawn by the combination in each case respectively will be :

• A. 50 watt, 100 watt
• B. 100 watt, 50 watt
• C. 200 watt, 150 watt
• D. 50 watt, 200 watt

Answer 1

Answer: (D)

$R=\frac{V^2}{P}=\frac{220\times 220}{100}=484\Omega$
In series, $R_{eq}=484+484+968\Omega$
$\therefore P_{eq}=\frac{V^2}{968}=\frac{220\times 220}{968}=50$ watt
In parallel, $R_{eq}=242\Omega$
$\therefore P_{eq}=\frac{V^2}{242}=\frac{220\times 220}{242}=200$ watt.