Question

An electric bulb has a rating of 100 W, 200 V. If the supply voltage drops to 100 V, The total heat and light energy produced by the bulb in 20 minutes is

• A. 10 KJ
• B. 20 KJ
• C. 30 KJ
• D. 40 KJ

Answer 1

The correct option is C 30 KJ

$\Rightarrow R=\frac{V^2}{P}=\frac{200\times 200}{100}=400$

$Q=\frac{V^2\times t}{R}$

$=\frac{100\times 100}{400}\times 20\times 60$

$=30000J$

$=30KJ$