Why does the current through an inductor decrease with time?

Answer:

When a current flows through an inductor, it creates a magnetic field around the inductor.

This magnetic field stores energy in the inductor.

When the current through the inductor is interrupted, the magnetic field collapses and releases this stored energy back into the circuit.

This causes a voltage to be induced across the inductor that opposes the change in current.

This phenomenon is known as inductive reactance.

The rate of change of current through an inductor is proportional to the voltage across it and inversely proportional to its inductance.

Therefore, when the voltage across an inductor is constant, the rate of change of current decreases with time as the magnetic field around it builds up and opposes the change in current. This results in a decrease in current through the inductor with time.