INEL 15140 Capacitance

Polarized capacitors can only be used in __ circuits.

DC

Capacitor

Devices that oppose a change of voltage.

Factors that determine capacitance:

The surface area if the plates, the distance between plates, the type of dielectric used.

Leakage Current

When electrons eventually move through the dielectric from the negative plate to the positive causing it to discharge. This current is proportional to the resistance of the dielectric and the charge across the plates.

A capacitor stores energy in an ________ field.

Electrostatic

Farad

The basic unit of capacitance. A capacitor has a capacitance of 1 farad when a charge of 1 volt across its plates results in a movement of one coulomb.

Q = C(V)

RC time constant

The amount of time needed to charge the capacitor in an RC circuit.

T = R(C)

Polarized Capacitors

Generally referred to as electrolytic capacitors. They’re sensitive to polarity and have one terminal identified as positive or negative.

Variable Capacitance

Their capacitance value can be changed over a certain range.

Capacitive Reactance

As a capacitor is charged an impressed voltage is developed across its plates as an electrostatic charge is built. The impressed voltage opposes the applied voltage and limits the flow of current in the circuit. The counter voltage developed by the capacitor is called reactance also.

There is no ____ power in a capacitive circuit.

True.

Capacitive and Inductive Vars are ___ out of phase with eachother.

180*