Question

Three bulbs B1 , B2 and B3 are connected to the mains as shown in the figure. How will the incandesence of the bulb B1 be affected, if one of the bulb B2 or B3 is disconnected from the circuit

• A. No change in the incandesence
• B. Bulb B1 will become brighter
• C. The bulb B1 will become less brighter
• D. The bulb B1 may become brighter or dimmer depending upon the candle power of the bulb which is disconnected

Answer 1

The correct option is C The bulb B1 will become less brighter

Equivalent resistance in a parallel combination is less than all it's constituents.
Therefore removing anyone of $B_2$, $B_3$ will increase the overall resistance of the circuit decreasing the current and as a result the brightness of $B_1$.