Question

Three bulbs of 40 W, 60 W, and 100 W are arranged in series with a 220 V source. The maximum light is obtained from

• A. 40 W
• B. 60 W
• C. All give the same light
• D. 100 W

Hint:

In a series circuit, the power dissipated is related to the resistance of the bulb, with higher resistance bulbs giving more light in the case of identical current.

Answer 1

The Correct Option is A

In a series circuit, the power dissipated by each bulb depends on its resistance, and the voltage across each bulb is proportional to its resistance. We know that the power \( P \) of a bulb is given by the formula: \[ P = \frac{V^2}{R} \] Where: - \( P \) is the power of the bulb, - \( V \) is the voltage across the bulb, - \( R \) is the resistance of the bulb. For the same current, the power dissipated by each bulb in a series circuit is inversely proportional to its resistance. A bulb with a higher power rating will have a lower resistance, meaning the lower power bulbs will dissipate more power.
Thus, the bulb with the least power rating (40 W) in a series circuit will actually give the maximum light due to its higher resistance compared to the other bulbs.
Thus, the maximum light is obtained from the \( 40 \, W \) bulb.