When current through an inductor begins to change, it cannot change instantaneously. Which fundamental effect prevents an instantaneous change in inductor current?

Introduction / Context:
Inductors resist changes in current. This time-dependent behavior governs the shape of transients in RL circuits, the operation of switching converters, and the design of snubbers. The physical reason is the voltage that the inductor itself produces whenever its current changes.

Given Data / Assumptions:

• An inductor with inductance L is part of a circuit where current is changing.
• We are considering short time intervals around the change.
• Core remains unsaturated; linear behavior assumed.

Concept / Approach:
An inductor obeys v_L = L * di/dt. A rapid attempted change in current (large di/dt) generates a large induced voltage whose polarity opposes the change (Lenz’s law). This self-induced or “counter” emf fights the change, limiting di/dt to a finite value set by circuit conditions.

Step-by-Step Solution:
Consider a sudden step in applied voltage across L.Inductor produces v_L that maintains current continuity: di/dt = v_L / L.As di/dt increases, v_L increases in opposing polarity, preventing an instantaneous jump in current.Thus, the counter emf of the coil is the effect that limits the rate of change of current.

Verification / Alternative check:
In an RL step response, current follows i(t) = I_final * (1 - e^(-t/τ)), where τ = L/R, clearly not instantaneous. The exponential rise or decay arises from the inductor’s induced voltage opposing current change.

Why Other Options Are Wrong:
Fixed resistance affects steady-state current and time constant but does not forbid instantaneous change by itself.

Applied emf drives current; it does not limit change.

Eddy currents and dielectric absorption are secondary effects and not the primary cause of current continuity in L.

Common Pitfalls:
Thinking an inductor “blocks DC.” It does not block steady DC; it resists changes in current. After transients settle, an ideal inductor behaves like a short circuit.

Final Answer:
the counter emf of the coil