Lenz's law
The induced current (or induced magnetic field) opposes the change in magnetic flux that causes it. Mathematically, this is reflected in the negative sign in Faraday's law: EMF = -dΦ/dt.
Real World
Eddy current braking on Eurostar trains uses Lenz's law: induced currents in the metal rail create a magnetic force opposing the train's motion, slowing it smoothly without mechanical contact.
Exam Focus
For 'explain' questions, always link Lenz's law back to energy conservation — state that the opposing force means work must be done against it.
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