Question

A circuit consists of three identical lamps connected to a battery as shown in the figure. When the switch $S$ is closed then the intensities of lamps $A$ and $B$

• A. will increase by eight times
• B. will decrease by two times
• C. will increase by more than two times
• D. will remain the same

Answer 1

Answer: (C)

After the closing of $S,C$ bulb or lamp become short-circuited

the potential across $A$ and $B$ before the closing of $S=\frac{V}{3}$
Potential across $A$ and $B$ after the closing of $S=\frac{V}{2}$
As $P\propto V^2$
$\therefore \frac{P_i}{P_f}=\frac{4}{9}$
$P_f=\frac{P_i\times 9}{4}=2.25P_i$