Question Analysis: Assertion (A) and Reason (R) type question based on Electromagnetic Induction.
Step 1 (Governing Law & Principle): [0.5 Mark]
The phenomenon is governed by Lenz's Law, which states that the polarity of induced emf is such that it produces a current whose magnetic field opposes the change in magnetic flux that produced it. Mathematically, the induced emf ($\varepsilon$) is given by:
$$\varepsilon = - \frac{d\phi_B}{dt}$$where $\phi_B$ is the magnetic flux linked with the coil.
Step 2 (Step-by-Step Logical Deduction): [0.25 Mark]
- When the circuit is closed, the motion of the magnet changes the magnetic flux linked with the coil, inducing an emf and a resulting current.
- According to Lenz's Law, this induced current creates a magnetic pole on the face of the coil that opposes the motion of the magnet (e.g., if the North pole approaches, the coil face becomes North to repel it).
- Because the coil has a large number of turns ($N$), the induced emf ($\varepsilon = -N \frac{d\phi}{dt}$) and the resulting current are significant, leading to a strong repulsive force that makes it physically difficult to push the magnet into the coil.
Step 3 (Final Concluded Answer): [0.25 Mark]
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
💡 EL10 Concept Insight: Think of the coil as a stubborn person who hates change; when you try to push a magnet in, the coil creates a magnetic "shield" to push back against you, and the more turns the coil has, the stronger that shield becomes!