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The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of 100 ~W and 200 ~V lamp when not in use?

Options

  1. A40
  2. B20
  3. C400
  4. D200

Correct answer

A. 40

Step-by-step solution

R_ hot = V^2 P = 200 200 100 =400 cold resistance =R_ hot / 10=400 / 10=40

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