Work Done Moving Magnet and Induced Current – Rankers Physics

Lenz Law: Practice Problem & Solution

Assertion (A): If a bar magnet is moved towards a conducting coil in a direction perpendicular to the plane of coil, the work done in moving the magnet will be more if it is moved faster rather than slower. Reason (R): If the magnet is moved at a faster rate towards the circular coil, then the induced current in the circular coil is more.  
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Lenz Law. Understanding the underlying formula is key to arriving at the correct answer below:

Assertion (A) is true: Faster movement causes a greater rate of change of magnetic flux (\(\frac{d\Phi}{dt}\)), leading to a larger induced emf (\(epsilon = -\frac{d\Phi}{dt}\)) and current (\(I = \frac{\epsilon}{R}\)). This results in a stronger opposing force (Lenz's Law), requiring more work. Reason (R) is true: Induced current is directly proportional to the rate of change of flux. Reason (R) correctly explains Assertion (A).

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