Several electric bulbs designed to he 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 220V line of the maximum allowable current is 5A ?

Explanation

Given potential differenc (V)=220V
Power input(P)=10W
Allowable electric current (I)=5A
Number of lamps connected in parallel=?
To calculate this first of all resistance of each of the lamp is to be calculated
we know `P=V^2-:R`
Hence, 10W=`(220V)^2-:R`
Or , R=`48400-:10W=4840Omega`
Let x bulb are to be connected in parallel to have eletric current equal to 5A
There, `1/R=1/(12Omega)+1/(6Omega)=(1+2)/(12)Omega=33/(12)Omega=1/4Omega`
Effective resistance `R=(4840)/xOmega`
We know that, `R=V/I`
`implies(4840)/xOmega=(220V)/(5A)`
`impliesx=(4840xx5)/(220)=110`
Thus, total 110 bulbs need to be connected in parallel