Practice question · Multiple choice
Lenz’s law says the induced current opposes the change producing it. What goes wrong if it reinforced the change instead?
Hints
- Follow the feedback loop round twice.
- Ask where the extra energy would be coming from.
Show the answer
D. Energy would appear from nothing, so the sign is conservation
Why
Reinforcement would be a runaway. The minus sign in Faraday’s law is not bookkeeping, it is what stops the universe containing free-energy machines.
Practise Electromagnetic Induction and Faraday's Law
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