Question

30 bulbs are connected in a series. If one bulb is fused and the remaining 29 bulbs are joined in a series and connected to the same supply, the light in the room will be:

• A. increased
• B. decreased
• C. remain same
• D. none

Answer 1

The correct option is A increased

Suppose a single bulb has resistance $R$ and the supply is of $V$ volts, then

in CASE-$1$

Equivalent resistance of $30$ such bulbs in $series$ will be $30\times R=30R$

Thus power in this case will be $P_1=\frac{V^2}{Resistance}=\frac{V^2}{30R}$ ........................ (1)

in CASE-$2$

Equivalent resistance of $29$ such bulbs in $series$ will be $29\times R=29R$

Thus power in this case will be $P_2=\frac{V^2}{Resistance}=\frac{V^2}{29R}$ ........................ (2)

We can see that $P_2>P_1$

so the light in the room will get $increased.$