CBSE Class 11-science Answered

Here  V = 220 V

          P = 10 W

          I = 5A

Resistance of each lamp R = V² / P =(220 x220) /10

                                                R = 4840 ohm

Now, let n number of lamps be connected in parallel of resistance R each

So equivalnt resistance = R' = R/n = (4840/n)ohm

Using V = IR' , we get

220 = ( 5 x 4840) / n

or n = ( 5 x 4840) / 220

      n = 10

Thus 10 lamps can be connected in parallel with each other across the two wires of 220 volt if the maximum allowance of current is 5 A.