Consider an inductive circuit in the time domain. The equivalent frequency domain circuit is obtained by replacing the resistance and inductance with their impedances.

The circuit is connected to an input with variable frequency, and the output is taken across the inductance.

 The output-to-input voltage division determines the transfer function.

 The expression of the transfer function gives the magnitude and phase derived from it.

The ratio of inductance to resistance is equal to the time constant of the inductive circuit.

The magnitude and phase can be written in terms of the time constant.

As the frequency approaches zero, the transfer function approaches zero, and the phase shift approximates pi over two.

When the frequency equals the inverse of the time constant, the amplitude reaches about 0.707 times its maximum value, and the phase shift is pi over four.

Similarly, at higher frequencies, the transfer function approaches unity, and the phase shift tends to zero.

These points, among a few additional ones, depict the frequency response through amplitude or magnitude and phase response graphs.