Electromagnetic Induction Principle

Steps:

• Identify the core mechanism: A simple A.C. generator relies on Faraday's law of electromagnetic induction to produce emf.
• Recall the setup: A magnet provides the magnetic field, and relative motion between the field and a conductor induces emf.
• Determine the conductor: In generators, a coil of wire rotates in the magnetic field to generate alternating current.
• Confirm the result: This motion changes magnetic flux through the coil, inducing alternating emf.

Why B is correct:

• Faraday's law states that induced emf equals the rate of change of magnetic flux linkage, which occurs when a coil of wire moves relative to a magnetic field.

Why the others are wrong:

• A. Battery: Provides direct current but does not induce emf through motion; it's a power source, not a generator component.
• C. Voltmeter: Measures voltage but plays no role in inducing emf.
• D. Relay: Switches circuits electromagnetically but does not generate induced emf.

Final answer: B