Question

Several electric bulb design to used on a 220V eletric supply line are rating 10W . How many lambs can be connect in parallel with each other across two line of 220V.if the max current 5A

Answer 1

here V=220V     P=10W     I=5A
step 1: resistance of each lamp  R=V²/P
R=220*22o/10
R=4840Ω
step2: let n be the no. of lamps connected in parallel, each of resistance R
therefore equivalent resistance of the parallel combination of 'n' lamps.
R'=R/n
4840/nΩ
V=IR'
220=5*4840?n
n=5*4840/220
n=110
thus 110 lamps can be connected in parallel to each other across the two wires of 220V.