Question

Two bulbs 60 W, 220 V and 100 W, 220 V are connected in series to a 440 V supply. Which of the two bulbs fuses? What happens if these bulbs are connected in parallel?

Answer 1

Answer:

Power, P=V

2

R

R

1

=

50

220×220

=968Ω

R

2

=

100

220×220

=484Ω

The equivalent resistance in the circuit,

R

eq

=R

1

+R

2

R

eq

=968+484=1452Ω

The current flow in the circuit,

I=

1452

440

=0.3030A

The voltage drop across bulb 1.

V

1

=iR

1

=0.3030×968=293.33V

The voltage drop across bulb 2.

V

2

=iR

2

=0.3030×484=146.65V

Bulb 1 will be fused because it can tolerate only 220 V but the voltage drop across it is 293.33V