Topic: Network Theory
An electric iron designed for 110 V AC supply was rated at 500 W. It was put across a 220 V supply. Assuming that at 110 V it supplied 500 W output (i.e. no losses) at the new voltage will supply
- A. 2500 W
- B. 250 W
- C. 500 W
- D. 2000 W
Answer: D. 2000 W
Explanation: Practically electric iron should be damaged. But as option we can calculate ideally as $R=\frac{V^{2}}{P}=\frac{110\times110}{500}=24.2~\Omega$. $P_{new}=\frac{V^{2}}{R}=\frac{220\times220}{24.2} \text{ Watt} = 2000~W$.