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Flux -time; emf -time graphs Faraday, Lenz

AQA Alevel Physics past paper p2, 2023 Q22. We are asked to choose graph of induced emf against time after being given graph of Flux against time. The answer is A, but my question is: shouldn't the line in the first section of the answer be negative & the line in the third section positive since Emf= - (minus) change in flux over time ? Lenz law, no? Now I'm totally confused after thinking I had understood it. Thanks

Reply 1

lordaxil

The negative sign is only meaningful if V and Φ have already been defined to be positive in the appropriate directions. The most important thing is that the initial and final emfs are in opposite directions.
see e.g. https://isaacphysics.org/concepts/cp_lenzs_law