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Which law states that the induced electromotive force in any closed circuit is equal to the negative of the time rate of change of the magnetic flux through the circuit?
Lenz's Law
Faraday's Law
Ampere's Law
Gauss's Law
Faraday's Law
Faraday's Law of Induction states that the magnitude of the induced electromotive force (EMF) in a circuit is directly proportional to the rate of change of magnetic flux through that circuit. The negative sign indicates that the direction of the induced EMF opposes the change in magnetic flux, which is an expression of Lenz's Law.
Faraday's Law of Induction states that the magnitude of the induced electromotive force (EMF) in a circuit is directly proportional to the rate of change of magnetic flux through that circuit. The negative sign indicates that the direction of the induced EMF opposes the change in magnetic flux, which is an expression of Lenz's Law.
Think of a water pump where the flow of water (current) is only initiated when you rapidly move a plunger (changing magnetic flux); the faster you move it, the more pressure (EMF) you create.
F-M-R: Faraday = Magnetic flux Rate.
╬╡=тИТdtd╬жBтАЛтАЛ тАФ Faraday's law of induction where ╬╡ is EMF and ╬жBтАЛ is magnetic flux
╬жBтАЛ=тИлBтЛЕdA тАФ Definition of magnetic flux through a surface
When the magnetic flux through a closed loop changes (due to movement of a magnet or change in current), an electric field is generated. According to Faraday's discovery, this change in the magnetic field lines passing through the area bounded by the conductor exerts a force on charge carriers, creating a potential difference (EMF) across the circuit.
The negative sign is often attributed to Lenz's Law, representing energy conservation.
The phenomenon is the foundational principle behind electric generators and transformers.
Magnetic flux is measured in Webers (Wb).
Enables large-scale electrical power generation.
Allows for efficient voltage conversion via induction.
Eddy currents can lead to energy loss as heat in metallic cores.
Electric Generators
Induction Cooktops
Transformers
Lenz's Law (Option A) specifically provides the direction of the induced current but not the magnitude.
Ampere's Law (Option C) relates magnetic fields to electric currents.
Gauss's Law (Option D) relates electric flux to enclosed charge.
B is correct тАФ Faraday's Law defines the relationship between the time rate of change of magnetic flux and the resulting induced electromotive force.
In exams, always look for the word 'magnitude' for Faraday's law and 'direction' for Lenz's law.