Alexander Fufaev

Formula: Charging Capacitor

Current-time graph - charging a capacitor

Capacitor current

Capacitor current is the electric current that flows into the plate of the capacitor and thus builds up a voltage on the capacitor. This capacitor current decreases exponentially with time during the charging process, while the capacitor voltage \( U(t) \) increases exponentially.

Charging current

Charging current is the initial current that flows into the capacitor plate at time \( t = 0 \). Its value is given by the applied source voltage.


Electrical capacitance is a characteristic quantity of the capacitor and tells how many charges must be brought onto the capacitor to charge the capacitor to the voltage \( 1 \, \text{V} \).

Electrical Resistance

Resistor with resistance \( R \) connected in series with the capacitor. The resistor has an influence on how fast the capacitor can charge.


After the source voltage \(U_0\) is applied (switch is closed), the capacitor starts to charge. The charging current starts to flow through the circuit and decays over time \(t\).