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Capacitor is a two-terminal component designed to store energy in electric field. It consists of two isolated plates, such that no charge can pass between them. When an electron arrives to one plate, one electron leaves the other plate. As more electrons arrive, negative charge accumulates on one plate, and the same amount of positive charge accumulates on the other plate. Presence of positive charge means electron depletion.
Capacitance is denoted as C and it is measured in farads (F). Capacitance of one farad storing a charge Q of 1 coulomb at each plate causes a voltage V of 1 volt between the plates,
V = Q / C
Constant current through a capacitor increases the charge at a constant rate, which increases the voltage across the capacitor at a constant rate. Voltage is proportional to the integral of capacitor current, and current is time derivative of voltage,
I = C dV / dt
EveryCircuit displays animations of capacitor charges right in the schematic, which makes it easier to understand circuit operation. Adjust the current source value with the knob and note how it affects the slope of the voltage waveform. Flip the switch to discharge the capacitor through a resistor.
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