Question

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

• 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
$\frac{\frac{10}{11}A}{\frac{5}{11}A}=2$