In basic electromagnetism, when electrical energy is supplied to a coil (inductor), in which physical form is that energy primarily stored while current flows?

Introduction / Context:
Inductors are everywhere in electrical and electronics engineering: power supplies, filters, motor drives, and radio-frequency circuits. A core idea is how inductors store and release energy. Unlike capacitors, which store energy in an electric field, coils store energy in a magnetic field produced by current. Understanding this difference helps with safe design (e.g., snubbers across coils) and accurate analysis of transient behavior.

Given Data / Assumptions:

• A current-carrying coil (inductor) is energized by a source.
• We are interested in the intrinsic energy storage mechanism of the inductor.
• Ideal inductor assumptions for the concept; real parasitics do not change the fundamental storage mechanism.

Concept / Approach:
The energy stored by an inductor is associated with the magnetic field set up by current through its turns. As current increases, the magnetic field strengthens and energy increases; when current decreases, the collapsing field returns energy to the circuit. The well-known energy relation is E_L = 1/2 * L * I^2, where L is inductance in henries and I is current in amperes.

Step-by-Step Solution:
A current I flows through N turns, creating a magnetic field linking the coil.Magnetic energy density is proportional to the square of the field strength.Total energy stored in the inductor is E_L = 1/2 * L * I^2.Therefore, the energy is stored in the magnetic field surrounding the coil.

Verification / Alternative check:
When current through an energized coil is interrupted, a voltage spike appears that attempts to keep current flowing. This behavior is consistent with field energy being returned to the circuit as the magnetic field collapses (inductive kick). Snubber networks or flyback diodes are used to safely dissipate or recycle this energy.

Why Other Options Are Wrong:
Electrical/electrostatic fields describe capacitor energy storage, not inductor storage.

“Force field” is not a precise engineering term here.

Mechanical strain energy does not describe an inductor's normal operation.

Common Pitfalls:
Confusing the energy location (in the field) with dissipation in winding resistance. An ideal inductor stores but does not dissipate energy; real coils also have copper loss in series resistance.

Final Answer:
a magnetic field