A bulb is rated 40 W for a 220 V supply. The peak voltage of the supply is
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( 220\sqrt{2}\,\mathrm{V} \)
The voltage quoted for an ac supply, here 220 V, is its rms value. For a sinusoidal voltage the peak value is \( \sqrt{2} \) times the rms value. The power rating of the bulb is not needed.
\( V_m = \sqrt{2}\,V_{\mathrm{rms}} = 220\sqrt{2}\,\mathrm{V} \approx 311\,\mathrm{V} \)
Note: NTA picked this question from an NCERT (2026-27) example and changed the figures. Do not ignore NCERT while practising numericals.
NCERT (2026-27):
AC Voltage Applied to a Resistor – …
