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Reactance

<^< Average Peak and RMS Values | Course Index | Capacitive Reactance >^>

When alternating voltages are applied to capacitors or inductors the magnitude of the current flowing will depend upon the value of capacitance or inductance and on the frequency of the voltage. In effect, capacitors and inductors oppose the flow of current in much the same way as a resistor, the important difference being that the effective resistance (or reactance) of the component varies with frequency (unlike the case of a conventional resistor where the magnitude of the resistance does not change with frequency).

Reactance, like resistance, is simply the ratio of applied voltage to the current flowing. Thus:

X = V/I

where X is the reactance in ohms (Ω), V is the alternating potential difference in volts (V) and I is the alternating current in amps (A).

In the case of capacitive reactance (i.e. the reactance of a capacitor) we use the suffix, C, so that the reactance equation becomes:

X_C = V_C/I_C

Similarly, in the case of inductive reactance (i.e. the reactance of an inductor) we use the suffix, L, so that the reactance equation becomes:

X_L = V_L/I_L

<^< Average Peak and RMS Values | Course index | Capacitive Reactance >^>