The emf induced in a generator is due to the change in:

Question

BlackTom AI · Accepted Answer

The question asks what the emf induced in a generator is due to the change in.
Option a: The angle between the magnetic field and the normal to the loop. This is correct because the magnetic flux through the loop is Φ = B A cos(θ), where θ is the angle between B and the loop normal. As the generator rotates, θ changes, so cos(θ) and thus Φ changes with time, producing an emf via Faraday's law (emf ∝ -dΦ/dt).
Option b: The magnitude of the magnetic field of the permanent magnets. While a changing B can cause a changing flux, in typical generator operation the magnets provide a relatively constant B; the key change comes from orientation or geometry, not a simple change in B magnitude. Thus this option is not the best general description of the emf origin.
Option c: The induced current flowing around the loop. The induced current is the result of the emf, not the cause of its existence. Emf drives the current; it is not what induces the emf itself.
Option d: The area of the loop where the magnetic flux is getting through. In many generators the loop area is fixed; emf can also arise from changing flux due to rotation (angle), not necessarily from changing area. If the area were changing, that would contribute to flux change, but the standard explanation for a rotating generator emphasizes angle (orientation) changes.

The emf induced in a generator is due to the change in:单项选择题

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