A resistor develops \( 800\,\mathrm{J} \) of thermal energy in \( 20\,\mathrm{s} \) on applying a potential difference of \( 20\,\mathrm{V} \). Its resistance is
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \( 10\,\Omega \)
The heat developed (the thermal energy) in a resistor is \( H = V^{2}t/R \), so the resistance follows directly from the heat, the voltage and the time.
\( \displaystyle R = \frac{V^{2}\,t}{H} \)
\( \displaystyle R = \frac{(20)^{2} \times 20}{800} = \frac{8000}{800} = 10\,\Omega \)