Question

State whether given statement is True or False
In an ac circuit, power to the load peaks at the frequency at which the load impedance is the complex conjugate of the output impedance.

• A. True
• B. False

Answer 1

The correct option is A True

According to maximum power transfer theorem. In pure DC circuit maximum power transfer to the load when load resistance is equal to internal resistance.

But in case of AC circuit consider the circuit as shown in figure

$i=\frac{E}{Z+Z_L}$

Power delivered to load $P_L=I^{2}X$

$P_L=\frac{E^2}{{(Z+Z_L)}^2}{X}_L=\frac{E^2{X}_L}{[{(X+X_L)}^2+{(Y+Y_L)}^2]}$

For maximum power transfer theorem

$Y+Y_L=0Y_L=-Y$

$X+X_L=2X_L{X}_L=XTherefore{Z}_L=X-IY$