Question

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

• A. Increases about 8 times
• B. Decreases by 2 times
• C. Increases about 2 times
• D. Remain same

Answer 1

Answer: (C)

Increases about 2 times

Answer 2

After closing of S C bulb or lamp become short circuited

∴ new circuit

=

potential across A and B before closing of S = $\frac{V}{3}$

Potential across A and B after closing of S = $\frac{V}{2}$

∴ $\frac{P_{i}}{P_{f}}$= $\frac{4}{9}$

P_f = $\frac{P_{i} \times 9}{4}$ = 2.1 P_i