A heating element is marked 210 V, 630 W. The resistance of the element would be
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → \( 70\,\Omega \)
The rating gives the power drawn when the element works at its rated voltage, and the electric power is \( P = V^{2}/R \).
\( \displaystyle R = \frac{V^{2}}{P} = \frac{(210\,\mathrm{V})^{2}}{630\,\mathrm{W}} = \frac{44100}{630}\,\Omega = 70\,\Omega \)