Capacitor Charge

 Capacitor Charge:

Define:

             The capacitor is fully charged when the voltage of the power supply is equal to that at the capacitor terminals.


Description:

This circuit shows the step response of an RC network. The step is generated at t=0, when the switch is closed. The initial voltage of the capacitor can be set.

V-I charateristic:


Capacitor voltage:

This formula is the result of a differential equation, as the current flowing in a capacitor is proportional to the derivative of the voltage applied to it.


Capacitor current:

This formula can be obtained again by solving a differential equation, or with the previous formula and then applying the Ohm's law.


RC time constant:

Also called tou , this constant gives the time required to charge the capacitor. In particular, after a time of 5RC the capacitor will reach the 99.3% of the input voltage step. while the 100% is an asymptotic value and will never be reached. So 5RC is usually the amount of time we consider enough to say that the capacitor is fully charged.


QUESTION:


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