Question

Two electric bulbs, one of $200\, V$, $40\, W$ and other of $200\,V$, $100 \,W$ are connected in a domestic circuit. Then

• A. resistance of 40 W bulb is more than 100 W bulb
• B. they have equal resistance
• C. the resistante of 100 W bulb is more than 40 W bulb
• D. they have equal current through them.

Answer 1

Answer: (A)

resistance of 40 W bulb is more than 100 W bulb

Answer 2

Using $P = \frac{V^2}{R}$ we get R = $\frac{V^2}{P}$ In domestic circuit, same voltage is applied across each bulb $\therefore \, R \propto \frac{1}{P}$ or $R_{40} \propto \frac{1}{40}$ and $R_{100} \propto \frac{1}{100}$ Clearly, resistance of 40 W bulb is more than 100 W bulb