Question

Some electric bulbs are connected in series across a $220v$ supply in a room. If one bulb is fused, then remaining bulbs are connected again in series across the same supply. The illumination in the room will

• A. not continuous
• B. remains the same
• C. decrease
• D. increase

Answer 1

The correct option is D increase

Step 1: Change of resistance
Suppose initial resistance of the combination is $R_s$
When one bulb fuses then equivalent resistance of the circuit,
$R_{eq}=R_s-R$
Where $R$ is the resistance of the fused bulb.
Hence, Equivalent resistance is decreased.

Step 2:Chaange of power
Given
$V=220V$
And we know,
$P=\frac{V^2}{R}$
For constant Voltage,
$\Rightarrow P\propto \frac{1}{R}$
Hence, If resistance is decreased, power will increase.
Hence option $\left(d\right)$ is correct.