Inductive Reactance

Author: E.E. Kimberly

According to equation 1-1, the instantaneous emf¹ generated in a coil by a varying current in that coil is

Also, if the flux linkages per ampere are constant,

Therefore,

If the current is i = Im sin co£,

When cos wt= 1,

Also,

or, as it is conventionally written,

(5-4)

The expression (2πfL) is called the inductive reactance of the circuit. The symbol for inductive reactance is XL, and it is expressed in ohms, as is resistance. Inductance is a property of a device or circuit. Inductive reactance depends on the inductance and also on the frequency.

1	In the equation -eL = N dθ/dt x 10-8, the minus sign is used because the voltage generated in the coil by changes in flux linkages is opposite in sense to the applied voltage causing the change in current which produces the change in flux.