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NDA 2019 GAT · General Knowledge · Current Electricity · hard

Two identical bulbs, each marked 220 V, 100 W, are connected in series across a 220 V supply. The total power consumed by the pair is

Single correct option

Two identical bulbs, each marked 220 V, 100 W, are connected in series across a 220 V supply. The total power consumed by the pair is
  1. A. 200 W
  2. B. 100 W
  3. C. 50 W
  4. D. 25 W
Show answer and solution

Answer: (C) 50 W

Resistance of each bulb is 220^2/100 = 484 ohm, so the series resistance is 968 ohm. Power = 220^2/968 = 50 W. Each bulb then gets only 110 V and glows dimly with 25 W. Reading 25 W gives only one bulb's share, and 200 W would be correct only for a parallel connection.
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Original question written in the NDA 2019 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