CBSE 2025 · Region 7 · Set 1 · Q24 · 3 marks
(a)State Faraday's law of electromagnetic induction and explain the role of negative sign in its expression.(b)Explain, with an example, that Lenz's law is consistent with the law of conservation of energy.
(a)
State Faraday's law of electromagnetic induction and explain the role of negative sign in its expression.
(b)
Explain, with an example, that Lenz's law is consistent with the law of conservation of energy.
Marking-scheme solution
(a)
Stating Faraday's law of electromagnetic Induction $\displaystyle 1$ Explaining the role of negative sign $\displaystyle 1$ (b)Explaining consistency of Lenz law with conservation of energy $\displaystyle 1$
(a)
The magnitude of induced emf in a circuit is equal to the time rate of change of magnetic flux.
\[\text { Mathematically, } \quad \mathrm{e}=-\mathrm{d} \Phi / \mathrm{dt}
\]
Negative sign indicates that the direction of induced emf and hence induced current in closed loop opposes its cause.
(b)
When magnet is moved closer/away from the loop, same/ opposite pole is developed on the approaching face of the loop. So, mechanical work is required to move a magnet which gets
Electromagnetic InductionFaraday’s Law of InductionUnderstandshort_answermedium
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CBSE Class 12 Physics past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.