To put this relationship between voltage and current in a capacitor in calculus terms, the current through a capacitor is the derivative of the voltage across the capacitor with respect to time. Or, stated in simpler terms, a capacitor’s current is directly proportional to how quickly the voltage across it is changing.
The product of the two yields the current going through the capacitor. If the voltage of a capacitor is 3sin (1000t) volts and its capacitance is 20μF, then what is the current going through the capacitor? To calculate the current through a capacitor with our online calculator, see our Capacitor Current Calculator.
In the next equation, we calculate the current across a capacitor. The current across a capacitor is equal to the capacitance of the capacitor multiplied by the derivative (or change) in the voltage across the capacitor. As the voltage across the capacitor increases, the current increases.
The flow of electrons onto the plates is known as the capacitors Charging Current which continues to flow until the voltage across both plates (and hence the capacitor) is equal to the applied voltage Vc. At this point the capacitor is said to be “fully charged” with electrons.
The property of a capacitor to store charge on its plates in the form of an electrostatic field is called the Capacitance of the capacitor. Not only that, but capacitance is also the property of a capacitor which resists the change of voltage across it.
The charge on a capacitor works with this formula: Q = C * V To compute changes in that charge (we call this the current), take the derivative dQ/dT = C * dV/dT + V * dC/dT Now proclaim the capacitance to be a constant, and that simplifies to dQ/dT = C * dV/dT = I (the current)