Capacitance Element in Series AC Circuit
- The voltage lags the current by a quarter of a period across a capacitor, f = –90 0 = –2p/4 = – p/2.
- A capacitor as a circuit element follows a modified form of Ohm's law, "V = R I"
Here XC is the effective ohmic resistance of the capacitor, called the capacitive reactance or more generally the impedance
- To find the voltage at any given moment in time one must multiply by the effective resistance XC by the current not at that moment but by the current in the capacitor T/4 seconds earlier, i.e. at t - T/4..
- Because the current is the derivative of the rate of change of the charge with time, the current in a capacitor has it greatest magnitude when the voltage is changing the greatest, and it is zero when the voltage is at its maximum or minimum value.
- The current in a capacitor is equal to the capacitance times the derivative of the voltage with respect to time.
- A capacitor cannot dissipate any energy loss in a series AC circuit. A capacitor only stores energy when is charged up and releases the energy when it discharges.
