In a purely capacitive A.C circuit, the current is:

Explanation

In a purely capacitive AC circuit, the current lags behind the electromotive force (emf) by 90 degrees. This means that the current reaches its maximum or minimum value 90 degrees after the voltage does. This phase difference occurs because of the behavior of capacitors in AC circuits. Capacitors store and release energy over time, causing the current to lag behind the voltage. Initially, when the voltage across the capacitor increases, the capacitor charges up, and current starts to flow. However, the rate at which the current increases is limited by the capacitance of the capacitor. As a result, the current takes time to reach its maximum value, causing it to lag behind the voltage by 90 degrees in a purely capacitive AC circuit.