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 ?

Explanation

V= 220 V
P 10 W
` P = (V^(2))/(R)`
`R = (V^(2))/(P)`
`= (220xx220)/(10)`
`4840 Omega`
V =IR
`R_(p) = (V)/(I) = (220)/(5) = 44Omega`
`R_(p) = (R)/(n) implies n = (R)/(Rp)= (4840)/(44) = 110`