Electromechanical energy conversion — generator principle: Which statement best describes the fundamental operating principle of an electric generator?

Introduction / Context:
Generators convert mechanical energy to electrical energy via electromagnetic induction. Recognizing the correct physical principle is crucial to understanding power generation and motor–generator reciprocity.

Given Data / Assumptions:

• Conventional generator with rotor motion in a magnetic field.
• No special construction details required.
• Basic Faraday–Lenz laws apply.

Concept / Approach:
By Faraday’s law, an electromotive force is induced in a conductor when the magnetic flux linking it changes. A simple way to achieve this change is to move the conductor through a magnetic field, producing an induced current in a closed circuit consistent with Lenz’s law.

Step-by-Step Solution:
Mechanically rotate or translate a conductor within a magnetic field.Changing flux linkage induces an EMF.If the circuit is closed, a current flows as the generator output.

Verification / Alternative check:
Flip the scenario for motors: apply current to a conductor in a magnetic field to produce force. This reciprocity affirms the generator principle conversely.

Why Other Options Are Wrong:
(a) and (c) refer to magnet pole interactions, not induction; (d) is the motor side of electromagnetism (field generation by current) rather than the generator’s cause of induced current.

Common Pitfalls:
Confusing cause and effect: a generator relies on motion in a field to induce current, not on the field produced by an already flowing current.

Final Answer:
Current is induced in a conductor that is moving through a magnetic field.