Question

Electric supply of a house is through a $10A$ fuse. When a $2000W$ heater is used in this house, how many $100W$ bulbs can be used simultaneously? The supply is at $220V$, and the heater and the bulbs are rated for $220V$.

• A. 2
• B. 3
• C. 4
• D. 5

Answer 1

The correct option is A

2

The current drawn by the 2000 W heater is
$I=\frac{P}{V}=\frac{2000W}{220V}=\frac{100}{11}A$
The maximum current the bulb can draw is
$10A-\frac{100}{11}A=\frac{10}{11}A$
Each bulb will take a current
$I=\frac{P}{V}=\frac{100W}{220V}=\frac{5}{11}A$
The number of bulbs that can be used is
$\frac{\frac{10}{11}A}{\frac{5}{11}A}=2$