Faraday's law
The quantitative law of electromagnetic induction: EMF = -N × dΦ/dt where N is the number of turns in the coil and dΦ/dt is the rate of change of magnetic flux through each turn. The negative sign indicates the direction (Lenz's law).
Formula
EMF = −N dΦ/dt
Real World
Every time a contactless payment card is held near a reader, the changing magnetic field from the reader induces an EMF in the card's coil via Faraday's law, powering the card's chip without a battery.
Exam Focus
Include the negative sign and define dΦ/dt clearly; in 'calculate' questions, show flux change divided by time, not just the final EMF value.
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