Solution

ID: past-exam-of-the-physics-2-paper-of-the-university-of-oxford/2021/11/a/solution

Faraday's law of induction states that the induced electromotive force around an oriented closed circuit equals the negative rate of change of linked magnetic flux. For a stationary circuit,
Here is electric field, is magnetic flux density, and the oriented surface has the circuit as its boundary. For identical series turns, replace by the total flux linkage . Lenz's law supplies the sign: an induced electric current opposes the change of linked magnetic flux, in agreement with conservation of energy.
If the wire moves with local velocity , the more general electromotive force includes the magnetic Lorentz force per unit electric charge:
The boundary and surface orientations in both expressions are related by the right-hand rule.

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