In a purely inductive circuit with a DC input after a long time, the inductor behaves as which?

In a purely inductive circuit with a DC input after a long time, the inductor behaves as which?

• A. A resistor.
• B. A capacitor.
• C. An open circuit.
• D. A short circuit.

Answer: (D)

In steady-state direct current, an inductor behaves as a short circuit. The key relationship is V = L di/dt. When the input is DC and enough time has passed, the current through the inductor becomes constant, so di/dt = 0. With no change in current, the voltage across the inductor drops to zero, meaning it offers essentially zero opposition to the current flow. In other words, it acts like a direct wire path, and the current is determined by the rest of the circuit rather than by the inductor itself. This is different from a resistor, which would impose a voltage drop for a given current, and from a capacitor, which blocks DC once fully charged.

In steady-state direct current, an inductor behaves as a short circuit. The key relationship is V = L di/dt. When the input is DC and enough time has passed, the current through the inductor becomes constant, so di/dt = 0. With no change in current, the voltage across the inductor drops to zero, meaning it offers essentially zero opposition to the current flow. In other words, it acts like a direct wire path, and the current is determined by the rest of the circuit rather than by the inductor itself. This is different from a resistor, which would impose a voltage drop for a given current, and from a capacitor, which blocks DC once fully charged.