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AIIMS2002PhysicsCurrent Electricity

An electric bulb marked 40 ~W and 200 ~V , is used in a circuit of supply voltage 100 ~V . Now its power is

Options

  1. A100 ~W
  2. B20 ~W
  3. C40 ~W
  4. D10 ~W .

Correct answer

D. 10 ~W .

Step-by-step solution

Actual power of bulb (P₁ )=40 ~W Actual voltage of bulb (V₁ )=200 ~V and supply voltage (V₂ )=100 ~V Power (P)= V^2 R V^2 . Therefore P₁ P₂ = V₁^2 V₂^2 or, 40 P₂ = (200)^2 (100)^2 =4 or P₂= 40 4 =10 ~W (where P₂= power when voltage is 100 ~V ).

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