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JEE Main202126 Aug 2021Evening ShiftPhysicsCurrent ElectricityActual

An electric bulb of 500 W at 100 V is used in a circuit having a 200 V supply. Calculate the resistance R to be connected in series with the bulb so that the power delivered by the bulb is 500 W .

Options

  1. A30   Ω
  2. B5   Ω
  3. C20   Ω
  4. D10   Ω

Correct answer

C. 20   Ω

Step-by-step solution

Resistance of bulb P = V 2 r r = ( 100 ) 2 500 = 100 × 100 500 = 20 i = P V = 500 100 = 5   A Δ V in resistance R = 100   V R = 100 5 = 20   Ω

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