Physics
Physics
Problem
(a) State Faraday’s law of electromagnetic induction and explain the physical significance of the negative sign that appears in the law. (b) A conducting ring is released from rest above a region that contains a uniform upward magnetic field whose magnitude decreases with time. Describe, with reasons, the direction of the induced current in the ring (i) while it is entering the field region, (ii) when it is completely inside the region, (iii) while it is leaving the region. (c) Why is no emf induced in the ring when it moves through a region where the magnetic field is uniform in both space and time, even though the field lines still pass through the ring?Intuitive explanation
Faraday's law connects changing magnetic flux to induced emf—the negative sign (Lenz's law) tells you that nature always opposes the change causing it, so the induced current creates a magnetic field that fights the flux change. The key insight is that emf depends only on how fast the flux through the loop is changing, not on the flux itself or how the change happens.
Intuitive explanation
Faraday's law connects changing magnetic flux to induced emf—the negative sign (Lenz's law) tells you that nature always opposes the change causing it, so the induced current creates a magnetic field that fights the flux change. The key insight is that emf depends only on how fast the flux through the loop is changing, not on the flux itself or how the change happens.