The minus sign in the expression for Faraday's law expresses
Correct answer: B. Lenz's law, that the induced effect opposes the change causing it
- A. that the emf is always negative
- B. Lenz's law, that the induced effect opposes the change causing it
- C. that flux always decreases
- D. an error of convention with no physical meaning
Explanation
The sign encodes the direction of the induced emf rather than its magnitude, stating that it acts to oppose the change in flux. Without it, an induced current could reinforce the change producing it and energy would be created from nothing. The magnitude of the emf is given by the rest of the expression.
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About Lenz's Law
Lenz's law states that the induced current flows in a direction that opposes the change in magnetic flux producing it. Questions connect this rule with Faraday's law, magnetic flux, induced emf and the direction of motion or current, while distinguishing opposition to flux change from opposition to the magnetic field itself.
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