Question

Several electric bulbs designed to be used on a 220 V electric supply line are rated 10 W. How many lamps can be connected in parallel with each other across the two wires of 220 V line if the maximum allowable current is 5 A?

Answer 1

In a parallel combination, each bulb has a voltage equal to that of the main line, and the sum of the currents drawn by each bulb would be equal to the allowable current.

From the given data,

Current flowing through each bulb
= ${\displaystyle \frac{\text{Wattage}}{\text{Voltage}}=\frac{10\text{W}}{220\text{V}}}$

= ${\displaystyle \frac{1}{22}\text{A}}$

Total maximum allowed current = 5 A

No. of bulbs which can be connected

= ${\displaystyle \frac{5\text{A}}{\frac{1}{22}\text{A}}}$

= 22 × 5

= 110

∴ Number of electric bulbs connected in parallel are 110.