Question

A boy has two spare light bulbs in his drawer. One is marked $240\, V$ and $100 \,W$ and the other is marked $240\, V$ and $60\, W$. He tries to decide which of the following assertions are correct ?

• A. The $60\, W$ light bulb has more resistance and therefore burns less brightly
• B. The $60\, W$ light bulb has less resistance and therefore burns less brightly
• C. The $100\, W$ bulb has more resistance and therefore burns more brightly
• D. The $100\, W$ bulb has less resistance and therefore burns less brightly

Answer 1

Answer: (A)

When the same potential difference, that is the voltage, is applied as in houses,
Power $=VI=\frac{V^{2}}{R}$
The smaller resistance consumes greater power. Here $100 \,W$ bulb has less resistance. It should glow more brightly. The $60 \,W$ bulb has more resistance