Physics
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Why is Lenz's Law a direct manifestation of the Law of Conservation of Energy?
My textbook states that the negative sign in Faraday's Law represents Lenz's Law and conservation of energy. What thought experiment best illustrates why an induced current must oppose its cause?
Recommended Answer by Tripti Mathur
Verified Educator
M.Tech (IIT Roorkee) • Physics Mentor
Consider proof by contradiction: If the induced magnetic field assisted rather than opposed the motion, pushing a North pole toward a closed coil would induce a South pole on that face. The coil would attract the magnet, causing continuous acceleration without external work!
This would generate unlimited kinetic energy from nothing, violating the First Law of Thermodynamics. Thus, the induced pole must be North to repel, ensuring work done equals electrical energy dissipated.
This would generate unlimited kinetic energy from nothing, violating the First Law of Thermodynamics. Thus, the induced pole must be North to repel, ensuring work done equals electrical energy dissipated.
Community Answers & Discussion (1)
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TMVerified Tutor • 46 mins agoConsider proof by contradiction: If the induced magnetic field assisted rather than opposed the motion, pushing a North pole toward a closed coil would induce a South pole on that face. The coil would attract the magnet, causing continuous acceleration without external work!
This would generate unlimited kinetic energy from nothing, violating the First Law of Thermodynamics. Thus, the induced pole must be North to repel, ensuring work done equals electrical energy dissipated.
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