Induced Current in a Ring – Rankers Physics

Lenz Law: Practice Problem & Solution

Assertion (A): A metal ring is kept on a cardboard on top of a fixed current carrying solenoid. If current in the solenoid is switched off, the upward reaction of card board on the ring will increase. Reason (R): Induced current in the ring will be in the same direction as in the solenoid.  
(1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
(2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(3) (A) is true but (R) is false
(4) 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:

When solenoid current is switched off, flux decreases. Induced current in the ring flows in the same direction as solenoid current (Lenz's Law), causing attraction. This increases the upward reaction.

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