Difficulty: Easy
Correct Answer: electricity, magnetism
Explanation:
Introduction / Context:Electromagnetic induction underpins generators, transformers, inductors, and many sensors. It explains how changing magnetic fields induce voltages and currents in conductors. Understanding the “from–to” relationship (what causes what) is foundational for both power and electronics domains.
Given Data / Assumptions:
Concept / Approach:Faraday’s law states the induced electromotive force in a coil is proportional to the negative rate of change of magnetic flux through it: e_induced = −N * dΦ/dt. In plain words, a changing magnetic field “through” a circuit produces (induces) an electrical voltage; if a closed path exists, current flows. Lenz’s law gives the polarity that opposes the change causing it. Therefore, electromagnetic induction is the generation of electricity (voltage/current) from magnetism (changing flux).
Step-by-Step Solution:
Identify the cause: varying magnetic flux linkage (by motion, varying current elsewhere, or both).Relate to effect: an induced voltage appears across the conductor or coil terminals.Conclude: the process converts magnetic-field change into electrical energy transfer (electricity).Apply to devices: generators (mechanical → magnetic change → electricity) and transformers (AC in primary → changing flux → induced voltage in secondary).Verification / Alternative check:Rotate a coil in a steady magnetic field: Φ varies sinusoidally with angle, creating a sinusoidal induced voltage. Alternatively, keep the coil still but vary the magnetic field (e.g., AC in a primary winding) and observe induced secondary voltage. Both confirm “electricity from magnetism.”
Why Other Options Are Wrong:
magnetism, electricity: describes the inverse (how electromagnets arise from current), not induction.electricity, electricity: omits the magnetic intermediary; that is conduction or amplification, not induction.magnetism, magnetism: self-referential; no energy conversion pathway.mechanical force, voltage: mechanical energy can create induction via motion, but the immediate cause in EM induction is changing magnetism, not force directly.Common Pitfalls:Confusing induction (changing flux → voltage) with the magnetic field created by current (current → magnetism). Also, assuming static magnetic fields induce voltage; it is the change (dΦ/dt) that matters.
Final Answer:electricity, magnetism
Discussion & Comments