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

Resistance `R_(1)` of the bulb is given by the expression,
Supply votage, V=220 V
Maximu,allowable current, I=5 A
Rating of an electric bulb P=10watts
Baceuse `R=V^(2)//P`
`R1=(220)^(2)/(10)=4840 Omega`
According to Ohm's law,
V=IR
Let R is the total resistance of the circuit for x namber of electric bulbs
`R=V//I`
`=(220)/5=44 Omega`
Resistance of each electric bulb, `R_(1)=4840 Omega`
`1/R=1/R_(1)+1/R_(2)+......"upto x time"`.
`1/R1/R_(1)xxX`
`X=R_(1)/R=(4840)/4=110`
`therefore` Number of electric bulbs connected in parallel are 110.