Electromagnetic Induction

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Chapter 25

• Electromagnetic Induction

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Michael Faraday b. Sept. 22, 1791, Newington,
Surrey, Eng. d. Aug. 25, 1867, Hampton Court
Found a current could be generated either by
moving a conductor through a magnetic field or by
moving a magnetic field past a conductor. This is
known as ELECTROMAGNETIC INDUCTION
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Faradays Experiments
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Fourth Right Hand Rule
Used to find the direction of the forces on the
charges in a conductor that is moving in a
magnetic field.
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Electromotive Force

• The potential difference, or voltage, given to
  the charges by a battery
• When you move a wire through a magnetic field,
  you exert forces on the charges and they move in
  the direction of the force. As you do this work
  on the charges their electrical potential is
  increased. This difference in potential is known
  as EMF.
• EMF BLv(sinq)

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EMF BLv(sinq)

• EMF electromotive force in volts
• B magnetic field strength in Teslas
• L length of wire in meters
• v velocity of the wire in m/s
• Sinq sin of the angle of the wire velocity to
  the magnetic field

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Electric Generator
As the wire spins in the magnetic field an
alternating current is generated
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Alternating Current Generators
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Lenzs Law

• The direction of the induced current is such that
  the magnetic field resulting from the induced
  current opposes the change in the field that
  caused the induced current.

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As the current increases through the wire the
magnetic field also increases
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Transformer device used to increase or decrease
AC voltage
Transformer Equation I is current, V is
Voltage, N is Number of Turns
P is Primary S is Secondary
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Homework

• Pages 690-693
• Numbers
• 30,31,35,49,75,and 53 (do as lab)