Question

When the filaments of higher resistance burns out, then intensity in.

• A. all three setting is 120 W
• B. all three setting is 60 W
• C. two setting is 60 W
• D. two setting is 120 W

Answer 1

The correct option is D two setting is 120 W

As $R=\frac{V^2}{P}$ so 60 W bulb has higher resistance. If it is burned out, there are two setting which will give 120 W power dissipation - a) either switch 1 is closed or b) both switch closed.