# AC Circuit Theory Maximum Power Transfer

I am currently hitting a barrier with regards to the basics of this question.

A 50HZ supply is connected to various given impedance's, calculate the maximum power transfer.

Maximum power transfer I understand is basically the Thevenin/Norton equivalent.

Though THERE IS NO EMF indicated in the question.

Is there a method around this problem (Calculate the Norton/Thevenin with only Impedance values)?

Any help would be superbly fantastic

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We need the specific structure of the circuit so that we can give you specific Hints. But the method for this question is, do the Thevenin analysis of your circuit: (1) Short circuit all emfs in the circuit and calculate the impedance at your terminals, (ii) calculate the $V_AB$ so that you have the Thevenin emf. The load therefore will have to match the internal impedance of your equivalent circuit, for maximum power transfer. Try it. – JKL Feb 23 '13 at 13:50

## 1 Answer

The Maximum Power Transfer Theorem is not so much a means of analysis as it is an aid to system design. Simply stated, the maximum amount of power will be dissipated by a load resistance when that load resistance is equal to the Thevenin/Norton resistance of the network supplying the power. If the load resistance is lower or higher than the Thevenin/Norton resistance of the source network, its dissipated power will be less than maximum.

This is essentially what is aimed for in radio transmitter design , where the antenna or transmission line “impedance” is matched to final power amplifier “impedance” for maximum radio frequency power output. Impedance, the overall opposition to AC and DC current, is very similar to resistance, and must be equal between source and load for the greatest amount of power to be transferred to the load. A load impedance that is too high will result in low power output. A load impedance that is too low will not only result in low power output, but possibly overheating of the amplifier due to the power dissipated in its internal (Thevenin or Norton) impedance.

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