The average ac current delivered to a circuit is zero.Despite this, power is dissipated in the circuit. How canthis be?The power is being dissipated in the magnetic field that isassociated with the current in the circuitO The power is being dissipated in both the electic and magneticfields that are associated with the currents and voltages in thecircuitO The power is being dissipated in the electric field that isassociated with the voltage in the circuitThe power dissipated in the circuit is proportional to thesquare of current, which is greater than or equal to zero.

The relation for the average power dissipated in an ac circuit is given by, P=VrmsIrmscosθ Here, P is the average power, Vrms is the rms voltage, Irms is the rms current and θ is the phase angle between voltage and current. Therefore, the power dissipated depends on the rms current through the ac circuit. The rms current is the square root of the mean of the squares of the instantaneous currents. Since ac current flows in alternate directions, the current can have positive and negative values. So, the average current through the ac circuit can be zero while the square of currents need not be always zero. Since the average power depends only on the rms current and not on the average current, power can be dissipated through an ac circuit. Hence, the fourth option is correct. The power depends on the rms voltage, the rms current and the phase angle. It is not important if the power is dissipated in the electric or magnetic fields. Hence, other options are incorrect.