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NDA 2018 GAT · General Knowledge · Current Electricity · medium

An electric bulb is rated 100 W, 200 V. The current drawn by the bulb when connected to a 200 V supply is

Single correct option

An electric bulb is rated 100 W, 200 V. The current drawn by the bulb when connected to a 200 V supply is
  1. A. 2 A
  2. B. 20 A
  3. C. 0.5 A
  4. D. 0.2 A
Show answer and solution

Answer: (C) 0.5 A

Power equals voltage times current, so I = P/V = 100/200 = 0.5 A. Giving 2 A comes from inverting the ratio, and 20 A or 0.2 A result from shifting the decimal point. The bulb's resistance would be V²/P = 400 ohm, which also gives 200/400 = 0.5 A and confirms the answer.
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Original question written in the NDA 2018 GAT pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake