Ch 21(1).ppt

# Magnetic flux faradays law of induction the induced

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Magnetic Flux

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Faraday’s law of induction: The induced emf is proportional to the rate of change of magnetic flux. [1 loop] [N loops] 21.2 Faraday’s Law of Induction;
The minus sign gives the direction of the induced emf : Lenz’s Law : A current produced by an induced emf moves in a direction so that the magnetic field it produces tends to restore the changed field. 21.2 Faraday’s Law of Induction; Lenz’s Law

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Induction of EMF How can we induce emf? Magnetic flux: What are the things that can change with time to result in change of magnetic flux? 1. Change of Magnetic Field 2. Change of the area 3. Change of the angle
EMF Induced on a Moving Conductor (changing area ) Induced emf using a U shaped conductor with a movable rod resting on it. As the rod moves at a speed v, it travels v Δt in time Δt, changing the area of the loop by ΔA=l (v Δt) B A t t Blv An emf induced on a conductor moving in a magnetic field is called a motional emf motional emf

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EMF Induced on a Rotating Coil (changing angle) The loop is rotating in a uniform B field with constant angular velocity ω The angle   Δ / Δ t  t The voltage (emf) generated is AC Sinusoidal with amplitude 0 =NBA US ac frequency is 60Hz. Europe is at 50Hz Most the U.S. power is generated at steam plants sin BA t sin NBA t 0 sin t
EMF Induced on a Rotating Coil (changing the angle ) What does a generator do? Transforms mechanical energy into the electrical energy What does this look like?

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