Question

Estimate the maximum number of identical bulbs whose power of each one = 40 W if they are
connected in parallel to a d.c. fused supply of emf, = 220 V if you know that the fuse cannot bear more than 5.5 A in surrounding temperature​

Answer 1

Let resistance of each bulb =R

When forty bulbs are connected in series I

1

=

40R

220

When 39 bulbs are connected in series I

2

=

39R

220

Here I

2

>I

1

As illumination depends upon power output, I

2

>I

1

makes I

2

2

R>I

1

2

R increasing brightness in second case.