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ELECTROMAGNETIC INDUCTION

ELECTROMAGNETIC INDUCTION. ELECTROMAGNETIC INDUCTION. Can a magnet produce electricity? Oersted’s experiments showed that electric current produces magnetic field.

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ELECTROMAGNETIC INDUCTION

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  1. ELECTROMAGNETIC INDUCTION

  2. ELECTROMAGNETIC INDUCTION Can a magnet produce electricity? Oersted’s experiments showed that electric current produces magnetic field. Michael Faraday discovered that when a magnet and a coil of wire are in relative motion wrt each other a current is induced in the coil. This phenomenon is called electromagnetic induction

  3. Faraday’s Experiment • A coil of wire is connected to a galvanometer. • A magnet is moved into the coil and taken out. • The galvanometer shows deflection.

  4. Faraday’s observations • Induced current is produced- whenever there is relative motion between the coil and the magnet. • The strength of the induced current depends on the rate of relative motion. • When the coil and magnet are at rest relative to each other there is no induced current.

  5. What is the cause of induced current? • Whenever there is relative motion between the coil and the magnet there is a change in the magnetic flux linked with the coil. When current through a coil continuously changes also a current is induced in a neighboring coil • The change in flux is the cause of induced current in the coil.

  6. Faraday’s Laws of Electromagnetic Induction • 1.Whenever there is a change in the magnetic flux linked with a coil a current is induced in it and the induced current exists as long as the change in flux exists. • 2. The strength of the induced current is proportional to the rate of change of flux. • I α dФ/dt

  7. Direction of induced current • The direction of induced current is so as to oppose the change in flux. I = - dФ/dt The direction is given by Lenz’s Law For a coil of N turns induced current is I = - N dФ/dt

  8. Lenz’s Lawand conservation of energy • Whenever the magnet is moved wrt coil work is done against either a force of attraction or repulsion . This work done is converted to Electrical energy. • When the N pole of magnet is moved towards coil induced current is anticlockwise.

  9. METHODS OF PRODUCING INDUCED CURRENT • Induced current is produced whenever the magnetic flux linked with a coil changes .The change in flux can be brought about in three ways. • The magnetic flux linked with a coil is Ф = B A sinθ. Flux changes when (i ) B changes ( ii ) A changes ( iii ) θ changes. (θ is the angle between B and the outward drawn normal to the plane of the coil). When there is relative motion between coil and magnet B changes.

  10. Induced e.m.f by changing area of coil linked with a magnetic field PQRS is a coil in a uniform magnetic field B. Side PQ is movable. Let PQ move with a velocity V through a small distance x. dA/dt = l dx/dt = -lv The e.m.f induced in the coil is E = - dФ/dt = - B dA/dt = Blv If the resistance of the coil is R then induced current is I = Blv/R.

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