For a thevenin equivalent circuit consisting of a voltage source Vg and an impedance Zg = Rg + jXg, i. show that the circuit delivers maximum average power to a load Zl = Rl + jXl when Rl = Rg and Xl = - Xg ii. show that maximum average power transfer theorem for ac circuits.( in both cases Vg and Zg are fixed and the load is variable)