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

here is ur answer.........

Answer 2

using formula, r = V²/P

where, V = 220 volts , P = 10 watt

so, r = (220)²/10 = 4840 Ω

hence, resistance of each bulb is 4840 Ω

according to Ohm's law, V = IR

let R is the equivalent resistance of the circuit for n number of bulbs.

so, R = V/I

here, V' = 220 volts and I = 5A

so, R = 220/5 = 44Ω

for parallel combination,

1/R = 1/r + 1/r + 1/r + ..... n times

= n/r

⇒n = r/R = 4840/44 = 110

hence, number of bulbs connected in parallel are 110.