Question

Three incandescent bulbs of $100W$ each are connected in series in an electrical circuit. In another circuit another set of three bulbs of the same wattage are connected in parallel to the same source.
(a) Will the bulb in the two circuits glow with the same brightness? Justify your answer.
(b) Now let one bulb in both the circuits get fused. Will the rest of the bulbs continue to glow in each circuit? Give reason.

Answer 1

Let us assume that resistance of each bulb is R

Case(1)

Current in each bulb $=\frac{V}{3R}$

case (2)

Net current $=\frac{3V}{R}$

Current will get equally divided in three bulbs $=\frac{I}{3}=\frac{V}{R}$

Bulbs in case (2) will glow with great brightness current $\propto$ Brightness

B) Now I one bulb gets fused, in case (9) rest of bulbs will not glow because in series voltage eruption in one appliance will affect other appliances.

But in case (b) all other bulbs will glow as voltage eruption in one bulb does not affect the voltage of other bulbs.