Question

Two bulbs rated 40 W, 220 V and 60 W, 220 V. Then which bulb will have more resistance:
1. 40 W, 220 V
2. 60 W, 220 V
3. Both will glow with equal brightness
4. Can't predict

Answer 1

Correct Answer - Option 1 : 40 W, 220 V

CONCEPT:

Electric power:

• The rate at which the electric energy is dissipated or consumed is termed electric power.
• The electric power is given as,

\(⇒ P=IV=I^{2}R=\frac{V^{2}}{R}\)

Where P = electric power, V = voltage, I = current and R = resistance

EXPLANATION:

Given P1 = 40 W, P2 = 60 W and V = 220 V,

• We know that for an electric bulb the resistance is given as,

\(⇒ R=\frac{V^{2}}{P}\)

\(⇒ R\propto\frac{1}{P}\)     -----(1)

• For an electric bulb, the resistance of the bulb is inversely proportional to the power of the bulb.
• So the bulb which has more power will have low resistance, therefore the 40 W bulb will have more resistance compared to the 60 W bulb.
• Hence, option 1 is correct.