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Electromagnetic Induction — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsElectromagnetic Induction3 Marks
Question
State the Lenz's law regarding electromagnetic induction. This law is based on the conservation law of which quantity?
A horizontal conducting wire of length 2 m oriented in east-west direction is falling down with a speed of 5 m/s perpendicular to the horizontal component of earth's magnetic field of $0.3 \times 10^{-4} T.$ Calculate the instantaneous value of induced emf across the ends of the wire.
✓

Answer

Lenz's Law : According to this law, "The direction of induced emf (or say induced current) in a circuit is such that it always opposes the cause or say change due to which it is produced."
In the mathematical expression of Faraday's second law of electromagnetic induction negative sign is the representation of Lenz's law.
This law is based on the law of conservation of energy.
Solution of Numerical question :
Instantaneous value of induced emf across the ends of the wire:
$e=Bvl \sin\theta \Rightarrow e=B_{H}vl \sin 90^{\circ}=B_{H}vl$
$e=(0.3 \times 10^{-4} T) \times (5 m/s) \times (2 m)$
$=0.3 \times 10^{-3} volt = 0.3 mV$

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