Inductor in DC circuits

In a DC circuit, the behavior of an inductor is quite different compared to an AC circuit. In an AC circuit, an inductor opposes changes in current by inducing a back EMF, while in a DC circuit, an inductor acts as a short circuit.

Explanation

To understand why an inductor acts as a short circuit in a DC circuit, let's consider the behavior of an inductor when a DC voltage is applied across it.

Inductor behavior with DC voltage
When a DC voltage is applied across an inductor, initially there is no current flowing through it. According to Faraday's law of electromagnetic induction, a change in magnetic field induces an electromotive force (EMF) across the inductor.

When the DC voltage is applied, the current starts to increase, and as the current increases, the magnetic field around the inductor also increases. This change in the magnetic field induces an EMF in the opposite direction, which opposes the applied voltage.

The opposition to the current change by the inductor is called inductive reactance. However, in a DC circuit, the rate of change of current is zero because the current is constant. Therefore, the inductive reactance is also zero.

Implication - Inductor acts as a short circuit
Since the inductive reactance is zero in a DC circuit, the inductor behaves as if it offers no opposition to the flow of current. In other words, the inductor acts as a short circuit.

When an inductor acts as a short circuit, the voltage drop across it is zero. Therefore, the entire applied voltage appears across the inductor terminals, resulting in a high current flow through it.

Conclusion
In a DC circuit, an inductor acts as a short circuit because there is no change in current and, consequently, no opposition to the current flow. This behavior is different from an AC circuit where an inductor opposes changes in current.