Asked in FBISE Physics 2022 SLO — Paper 2022Moderate

The source of emf transfers its maximum power to the external circuit when ( r = internal resistance and R = load resistance):

Correct answer: B. r = R

  • A. r = 0
  • B. r = R
  • C. r < R
  • D. r > R

Explanation

The condition for maximum power transfer from a source of emf to an external circuit occurs when the load resistance ( R ) is equal to the internal resistance ( r ) of the source. This is known as the Maximum Power Transfer Theorem, and it can be mathematically expressed as:R=rWhen this condition is met, the power transferred to the load is maximized.

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About Maximum Power Output

Maximum power output describes the condition in which a source with internal resistance delivers the greatest power to an external load. The topic uses P = I²R and related circuit equations to show that maximum power occurs when load resistance equals internal resistance. This differs from maximum efficiency, which occurs under a separate condition.

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