Question

Three identical bulbs are connected to a battery as shown in figure. When the circuit is closed by means of the switch S, it is found that

• A. R will be bright, but Q and P dim
• B. P, Q and R, all will be equally bright
• C. Q and R will immediately bum out
• D. P will be bright, but Q and R dim

Answer 1

The correct option is D P will be bright, but Q and R dim

When switch is closed, bulbs Q and R are in parallel and then the parallel combination (Q,R) and P are in series. As all are identical so they have equal resistances and current will more flow through P than of Q and R. The reason is that the current is divided into parallel branch. Since power $P=I^{2}R$ so P will be bright, but Q and R dim.