Electromagnetic induction
The generation of an electrical current or EMF when magnetic flux through a circuit changes. Faraday's law: EMF = −N(ΔΦ_B/Δt), where N is the number of turns, Φ_B is magnetic flux, and t is time. The negative sign (Lenz's law) indicates that the induced EMF opposes the change causing it. Electromagnetic induction is the principle behind generators, transformers, and many other electrical devices.
Formula
EMF = −N(ΔΦ_B/Δt)
Real World
Every time a wind turbine blade at an Ørsted offshore wind farm completes a rotation, the coils inside the generator cut through magnetic flux lines, inducing the EMF that ultimately powers homes across the UK.
Exam Focus
Always invoke Lenz's law to justify the direction of induced current — the negative sign alone scores nothing unless you explain the opposing effect.
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