Many electrical devices operate on the principle of electromagnetic ______.

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Electromagnetic induction is the production of voltage in a conductor when the magnetic field through that conductor changes. This changing magnetic flux induces an electromotive force, and therefore current, even without a direct electrical connection. This principle is what powers many devices: generators rely on rotating a coil in a magnetic field to produce electricity, and transformers depend on changing flux in one winding to induce voltage in another. Faraday’s law formalizes this idea: the induced EMF is proportional to the rate of change of magnetic flux. Lenz’s law then tells us the induced current will flow in a way that opposes the change that created it.

Conduction involves direct transfer of charge through a material with a closed path, which requires a physical connection. Reflection is about waves bouncing off a boundary, not energy transfer in circuits, and resonance is about a system’s amplified response at a specific frequency. None of those describe the broad mechanism by which many electrical devices operate through changing magnetic fields.