__Reactance__

The term

**reactance (X)**is the opposition to the flow of**ac currents**. As we have seen in the Higher course, for a**resistor**the opposition to current in dc and ac is the same. However we have seen how for both**capacitors**and**inductors**the opposition to current in ac varies with frequency and differs from that in dc.For the aside below refer to the wave equations learned in the

**Quanta and Waves**section:"y = Asin(2πft)"

From the expression of reactance, XL, is measured in ohms when V is in volts and I is in amperes.

The peak current is Ipk and Vpk = 2πfLIpk. From that, the inductor’s reactance is worked out as:

So:

For a Capacitor(Capacitive Reactance) | For an Inductor(Inductive Reactance) |