Maximum power transfer theorem

Maximum Power transfer theorem:

• In electrical engineering, the maximum power (transfer) theorem states that, to obtain maximum external power from a source with a finite internal resistance, the resistance of the load must be made the same as that of the source. It is claimed that Russian engineer Moritz von Jacobi was first to discover the maximum power (transfer) theorem around 1840, which is also referred to as "Jacobi's law".
• The theorem results in maximum power transfer, and not maximum efficiency. If the resistance of the load is made larger than the resistance of the source, then efficiency is higher, since a higher percentage of the source power is transferred to the load, but the magnitude of the load power is lower since the total circuit resistance goes up.
  
  
  
• If the load resistance is smaller than the source resistance, then most of the power ends up being dissipated in the source, and although the total power dissipated is higher, due to a lower total resistance, it turns out that the amount dissipated in the load is reduced.
• The theorem can be extended to AC circuits which include reactance, and states that maximum power transfer occurs when the load impedance is equal to the complex conjugate of the source impedance.