Electronics Principles V11

Clive W. Humphris

CAPACITORS: Capacitor Reactance.  

Capacitive reactance is the opposition to the applied voltage change. The symbol Xc is used and expressed in Ohms.

Capacitive reactance decreases with increasing frequency and is therefore inversely proportional to the capacitance. This relationship between frequency and capacitive reactance is opposite to that for an inductor.

The graph shows an accurate representation of the capacitor reactance over a typical range of frequencies. This is included to enable the response curve to be plotted. For very low frequencies the reactance will be extremely high, effectively open-circuit. For increasing frequency the capacitor reactance falls, exponentially.

This is opposite to the effect on an inductor, where the inductive reactance increases with applied frequency in a straight line.

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