Four ways to induce an EMF — all change the flux linkage

Electromagnetic Induction — AQA A-Level Physics

There are several methods for inducing an EMFElectromotive force. The energy transferred per unit charge by a source in driving charge around a complete circuit. Measured in volts (V)., but they all share the same underlying physics: you change the flux linkageThe product of magnetic flux and the number of turns of a coil. Measured in weberThe SI unit of magnetic flux. One weber is the flux through an area of 1 m² when the magnetic flux density is 1 T perpendicular to the area.-turns (Wb turns). NΦ through a circuit. Here are the main ones.
Moving a wire through a magnetic field. The wire sweeps out area, changing the flux through the circuit it's part of.
Moving a magnet into or out of a coil. The flux through the coil increases or decreases as the magnet approaches or retreats.
Changing the currentThe rate of flow of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. Measured in amperes (A). in a nearby coil (mutual induction). CurrentThe rate of flow of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. Measured in amperes (A). in one coil produces a magnetic field. If that currentThe rate of flow of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. Measured in amperes (A). changes, the field changes, and the flux through a second nearby coil changes too. This is how transformers work.
Rotating a coil in a magnetic field. The angle between the coil's area vector and the field changes continuously, so the flux linkageThe product of magnetic flux and the number of turns of a coil. Measured in weberThe SI unit of magnetic flux. One weber is the flux through an area of 1 m² when the magnetic flux density is 1 T perpendicular to the area.-turns (Wb turns). changes sinusoidally. This is the principle behind AC generators.
You can also induce an EMFElectromotive force. The energy transferred per unit charge by a source in driving charge around a complete circuit. Measured in volts (V). by changing the field strength itself (e.g. with an electromagnet) or by changing the area of the circuit. All reduce to the same thing: ΔΦ/Δt.

Examiner Tips and Tricks

If an exam question asks 'how could the EMFElectromotive force. The energy transferred per unit charge by a source in driving charge around a complete circuit. Measured in volts (V). be increased?', the answer always comes back to Faraday's lawThe magnitude of the induced EMF is proportional to the rate of change of magnetic flux linkageThe product of magnetic flux and the number of turns of a coil. Measured in weberThe SI unit of magnetic flux. One weber is the flux through an area of 1 m² when the magnetic flux density is 1 T perpendicular to the area.-turns (Wb turns)...
Increase the rate of change of flux linkage: move faster, use a stronger field, use more turns, or increase the area of the coil.