Question

Two electric bulbs marked $60W,220Vand100W,220V$ are connected in series to a $440V$ supply. Which of the bulbs is more likely to get fused ?

• A. $60Wbulb$
• B. $100Wbulb$
• C. Neither of the bulbs
• D. Both the bulbs

Answer 1

The correct option is A $60Wbulb$

Power, $P=V^{2}R$

$R_1=\frac{220\times 220}{50}=968\Omega$

$R_2=\frac{220\times 220}{100}=484\Omega$

The equivalent resistance in the circuit,

$R_{eq}=R_1+R_2$

$R_{eq}=968+484=1452\Omega$

The current flow in the circuit,

$I=\frac{440}{1452}=0.3030A$

The voltage drop across bulb 1.

$V_1=i{R}_1=0.3030\times 968=293.33V$

The voltage drop across bulb 2.

$V_2=i{R}_2=0.3030\times 484=146.65V$

Bulb 1 will be fused because it can tolerate only 220 V but the voltage drop across it is 293.33V

The correct option is A.