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Electromagnetic Induction

Electromagnetic Induction. Faraday. Discovered basic principle of electromagnetic induction Whenever the magnetic field around a conductor is moving or changing magnitude, a current is induced in the conductor. Torus Ring.

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Electromagnetic Induction

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  1. Electromagnetic Induction

  2. Faraday • Discovered basic principle of electromagnetic induction • Whenever the magnetic field around a conductor is moving or changing magnitude, a current is induced in the conductor

  3. Torus Ring • When switch is turned on, a magnetic field is created in coil A and the entire iron ring becomes magnetized • Sudden increase in magnetic field causes a current to momentarily be induced in coil B • Once the field becomes steady in the ring, induced current no longer exits • When switch is turned off, the sudden demagnetization causes current to be again momentarily induced but in opposite direction

  4. Factors Affecting Current Induced • Number of loops • More loops, greater current • Rate of motion of magnetic field • Faster motion, greater current • Strength of magnetic field • Stronger field, greater current

  5. Faraday’s Law • Amount of emf induced is proportional to: • Rate of change in magnetic field (called flux) • Flux is directly proportional to B and A • Unit of flux is the Weber (Wb) •  = BA cos • Number of loops in the wire • Rate of change •  = -N (/t)

  6. Example • A conductive wire consisting of 3 loops and enclosing an area of .020 m2 is perpendicular to a uniform magnetic field of .030T. If the field goes to zero in .0045sec, what is the magnitude of the induced emf?

  7. Example • The magnetic flux through a 60 turn coil of wire is reduced from 35Wb to 5.0Wb in .10sec. The average induced current is .0036 A, what is the wire’s resistance?

  8. Direction • emf acts in direction opposite to the flux • Induced emf gives rise to current whose magnetic field opposes original field

  9. Lenz’s Law • Current flows in a direction such that the induced field they create opposes the action of the inducing field • Work done moving a magnetic field against its opposing force is transformed into electric energy

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