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JEE Main20198 Apr 2019Evening ShiftPhysicsCurrent ElectricityActual

A cell of internal resistance r drives current through an external resistance R . The power delivered by the cell to the external resistance will be maximum when:

Options

  1. AR = 2 r
  2. BR = r
  3. CR = 1000 r
  4. DR = 0.001 r

Correct answer

B. R = r

Step-by-step solution

Current i = E r + R Power generated in R P = i 2 R P = E 2 R ( r + R ) 2 for maximum power d P d R = 0 E 2 ( r + R ) 2 × 1 - R × 2 ( r + R ) ( r + R ) 4 = 0 ⇒ when,   r = R   then,  d P d R = 0

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