Question

a circuit has 5A . how many lamps of 40W;220V can simultaneously run on this line safety

Answer 1

Given current = 5 A , Pot. difference = 220v and Power of each lamp = 40w

Now let total no of lamps be N
then
Power × N = current × pot. difference
40×N = 220 × 5
N = 27.5
hence the no of lamps cannt be in fraction
so no of lamps = 27