Electromagnetism

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Electromagnetism
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Magnetic field around a current carrying conductor
Magnetic flux

• Grip rule If the conductor is gripped with
  right hand, with the thumb extended in the
  direction of current, the fingers wrapped around
  the conductor indicate the direction of field.

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Magnetic field produced by a solenoid

• Grip rule If the coil (solenoid) is gripped with
  the right hand, with the fingers pointing in the
  direction of current, then the thumb out-
  stretched parallel to the axis of the coil points
  in the direction of the magnetic field inside the
  solenoid

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Force acting on a Conductor

• A current carrying conductor, placed in a
  magnetic field, produces a force.
• This force can be increased,
• When the current in the conductor is increased
• When length of conductor is increased
• When the magnetic field is made stronger
• Force on the conductor
• f lux density ? length of conductor ? current
• or f B I l
  Newton
• Note considering single conductor

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Direction of Force Flemings left hand rule

• Mechanical force exerted on the conductor always
  acts in a direction perpendicular to the plane of
  the conductor and the magnetic field

This is the principle of electric motor
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Electromagnetic Induction

• An EMF is induced in a conductor if the following
  conditions are satisfied
• Magnetic field
• Conductor in the vicinity of magnetic field
• Magnetic field linking with conductor changes OR
  Relative motion between the Conductor Field
• Faradays laws of
• Electromagnetic Induction
• When a conductor cuts or it is cut by
• magnetic flux, an emf is induced in the
  conductor.
• The magnitude of the induced emf is proportional
• to the rate at which the conductor cuts or is
  cut by
• the magnetic flux

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Electromagnetic Induction

• Direction (Polarity) of induced emf
• Lenzs law
• An electro magnetically induced emf always acts
  in such a direction to set up a current opposing
  the motion or change of flux responsible for
  inducing the emf.

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Fleming's right hand rule
Right hand rule If the first finger of the right
hand is pointed in the direction of the magnetic
flux, and if the thumb is pointed in the
direction of motion of the conductor relative to
the magnetic field, then the second finger, held
at right angles to both the thumb and the first
finger represents the direction of emf.
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Induced emf

• Statically induced emf - The voltage induced in
  the conductor due to change in the magnetic field
  
• Conductor is stationary
• Magnetic Field is changing in a stationary
  Magnetic System
• Ex Transformer
• Dynamically induced emf - The voltage induced in
  the conductor due to relative motion of conductor
  and magnetic field
• Conductor is moving/stationary
• Magnetic Field is stationary/moving