Maximum power is transferred from a source to an external load when
Correct answer: B. the load resistance equals the internal resistance of the source
- A. the load resistance is much larger than the internal resistance
- B. the load resistance equals the internal resistance of the source
- C. the load resistance is zero
- D. the internal resistance is zero
Explanation
Matching the load to the internal resistance maximises the power delivered, though the efficiency at that point is only 50 per cent, since equal power is wasted inside the source. A power station therefore aims for high efficiency instead, keeping its internal resistance very low. Impedance matching in audio and radio systems is the same idea applied to alternating current.
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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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