# Behaviour of capacitor while charging

When a capacitor is applied with an AC Wave in a circuit containing only capacitor, it charges to its peak value between the time period of 0 to 90 degrees. My doubt is that what happens between the time period 90 to 180 degrees i.e. when the voltage starts decreasing from peak to zero. I understand that there is no dissipating element in the circuit therefore charge will not decay as time constant RC is zero. But still I was eager to know what happens at that time interval i.e. 90 to 180 degrees.

• The charge will decay; it'll go back into the voltage source. – Hearth Nov 25 '18 at 21:48
• No. It remains constant. What you are saying happens b/w 180 to 270 degrees. – John Cena Nov 25 '18 at 21:51
• Remember that current and voltage are out of phase in a capacitor. – Hearth Nov 25 '18 at 21:52
• I know that by 90 degrees. – John Cena Nov 25 '18 at 21:59
• @JohnCena, if the voltage on the capacitor falls, then the charge is dropping. $Q=CV$. You can't change $V$ without changing $Q$. – The Photon Nov 25 '18 at 22:00