Download Magnetic field Conductor

Electromagnetism
Magnetic field around a current carrying conductor
-
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.
ELE101/102
Dept of E&E,MIT Manipal
Magnetic flux
+
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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 outstretched parallel to the
axis of the coil points in
the direction of the
magnetic field inside the
solenoid
ELE101/102
Field
Dept of E&E,MIT Manipal
3
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
ELE101/102
Dept of E&E,MIT Manipal
4
Direction of Force: Fleming’s 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
thumb
(Mechanical force)
(First finger)
Field
(Second finger)
Current
This is the principle of electric
motor
ELE101/102
Dept of E&E,MIT Manipal
5
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
Faraday’s laws of
Electromagnetic Induction
1) When a conductor cuts or it is cut by
magnetic flux, an emf is induced in the conductor.
2) The magnitude of the induced emf is proportional
to the rate at which the conductor cuts or is cut by
the magnetic flux
ELE101/102
Dept of E&E,MIT Manipal
d
di
L
dt
dt
 N d  L di
d N 
LN

di
I
e N
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Electromagnetic Induction
Direction (Polarity) of induced emf:
Lenz’s 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.
ELE101/102
Dept of E&E,MIT Manipal
7
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.
ELE101/102
Dept of E&E,MIT Manipal
Motion
Field
(thumb)
(First finger)
Emf
(second finger)
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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
ELE101/102
Dept of E&E,MIT Manipal
e  Blv sin 
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