A pure capacitor is connected to an ac power supply. In this circuit, the current A) lags the voltage by 90 degree.
B) leads the voltage by 90 degree.
C) lags the voltage by 180 degree.
D) is in phase with the voltage.
E) None of the given answers are correct.

B) leads the voltage by degree.

Explanation:

The capacitor having capacitance is connected with the AC power supply as shown in the figure.

Let the voltage of the power source be

,

where is the angular frequency, represents time and is the maximum voltage. Here, and is constants.

At any instant, let be the charge on the capacitor and as the potential difference across the capacitor is , so .

As the current, , in the circuit is the rate of change of charge, , so

[from equation]

Now, from equations and , the phase difference between current and the voltage is where current is leading.

So, the current leads the voltage by or degree.

Hence, option is correct.

answer( sicar );