Download The earth is a giant magnet

The earth is a giant magnet
Magnetic field lines
of force
leave the north
pole and enter
the south pole.
What is a magnetic
field?
Magnetic field
The space around a magnet where
the forces of attraction and repulsion
act is the magnetic field. A magnetic
field is made up of lines of force.
What are poles?
The poles represent the part
of a magnetic field where the
magnetic forces appear to be
concentrated.
Magnetic flux patterns
Magnetic flux patterns
Magnetic?
These materials along
with certain other alloys are
called ferromagnetic materials.
Hard or soft material?
Iron has stronger induced
magnetism.
Steel has a weaker induced
magnetism.
Hard or soft?
Hard or soft?
Iron is a magnetically soft material.
Strong but temporary!
Steel is a magnetically hard material.
Weak but permanent!
Induced magnetism
Making magnets
Single touch method
The end where the stroking pole
leaves the bar
becomes the opposite pole.
Making magnets
Double touch method
The end where the stroking pole
leaves the bar
becomes the opposite pole.
Making magnets:
can a magnet have similar poles at its ends?
Consequent poles
The end where the stroking pole
leaves the bar
becomes the opposite pole.
The Domain Theory of magnets
Magnetic material
In demagnetized
condition
Dipoles in
magnetic
domains
Magnetic material
In magnetized
condition
Domain theory explains:
1. Demagnetization: mechanical vibrations can cause demagnetization
2. Magnetic saturation: strength of a magnet cannot be increased beyond a certain
limit.
3. Breaking a magnet: breaking a magnet
the broken ends maintain the poles.
Magnetic keepers
Magnetic effect of current
electromagnet
To tell the poles:
1. face the coil, trace the direction of current flow,
if it is anticlockwise then that is the North pole
If it is clockwise then that is the South pole
2.Use right hand grip rule,
the thumb points to the N, the end is the S
Direction of the magnetic field
Grip the wire with your right hand,
the field lines will go in the direction
of the fingers.
Magnetic effect of an electric current
Magnetic flux pattern due to a current
in a long straight wire,
Magnetic effect of an electric current
Use the right
hand grip rule
Magnetic flux pattern due to a current
in a short circular coil of wire.
Magnetic effect of an electric current
Magnetic flux
pattern due to a
current in a
solenoid.
Grip
the solenoid
with the right hand
with the fingers in
the direction
of the current
The thumb points
to the north pole
Direction of the magnetic field
Grip the wire with your right hand,
the field lines will go in the direction
of the fingers.
Kicking wire experiment
Force on conductor
Field due to
permanent
magnet
Field due to
current
in wire
Two fields interact
to produce
force (motion)
Fleming’s left hand rule
Used to determine
direction of motion of conductor
d.c. electric motor
Fields interact, coil turns
END OF MOTORS…
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u can not sleep if u don’t know it.
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