Home

.

Reactance

 

Inductive Reactance
The inductive reactance X
L of an inductance L at angular frequency
w
and frequency f is:
XL =
wL = 2p
fL

For a sinusoidal current i of amplitude I and angular frequency w:
i = I sinwt
If sinusoidal current i is passed through an inductance L, the voltage e across the inductance is:
e = L di/dt =
wLI coswt = XLI coswt

The current through an inductance lags the voltage across it by 90°.

Capacitive Reactance
The capacitive reactance X
C of a capacitance C at angular frequency
w and frequency f is:
XC = 1 /
wC = 1 / 2p
fC

For a sinusoidal voltage v of amplitude V and angular frequency w:
v = V sinwt
If sinusoidal voltage v is applied across a capacitance C, the current i through the capacitance is:
i = C dv/dt =
wCV coswt = V cosw
t / XC

The current through a capacitance leads the voltage across it by 90°.