Download Magnetic Fields

Magnetic Fields
By:
Engr. Hinesh Kumar
Lecturer
I.B.T, LUMHS
Magnetism
Since ancient times, certain materials, called
magnets, have been known to have the property of
attracting tiny pieces of metal. This attractive
property is called magnetism.
S
Bar Magnet
S
N
N
Magnetic Poles
Iron
filings
N
The strength of a magnet is
concentrated at the ends,
called north and south
“poles” of the magnet.
S
A suspended magnet:
N-seeking end and
S-seeking end are N
and S poles.
W
N
S
N
Bar magnet
S
N
E
Compass
Magnetic Attraction-Repulsion
attraction
repulsion
Magnetism is the force of ___________
or ___________
of magnetic materials.
Magnetic Attraction-Repulsion
S
S
N
N
N
Magnetic Forces:
Like Poles Repel
S
S
N
N
S
Unlike Poles Attract
Magnetic Field
• A field of force surrounding a permanent
magnet or a moving charged particle, in
which another permanent magnet or
moving charge experiences a force
• The lines of force surrounding a permanent
magnet or a moving charged particle.
• Its a vector quantity.
• Its units: Tesla, Gauss
Magnetic Field
magnetic field
A __________
______ is an area around a magnet that applies
a force to magnetic materials without touching them.
The magnetic field actually keeps going out forever, it just gets
weaker the farther away from the magnet it is.
It eventually gets too weak to move anything.
Magnetic Field Lines
We can describe
magnetic field lines
by imagining a tiny
compass placed at
nearby points.
The direction of the
magnetic field B at
any point is the same
as the direction
indicated by this
compass.
N
S
Field B is strong where
lines are dense and weak
where lines are sparse.
Properties
• Magnetic field lines are continuous
unbroken, forming closed loops.
and
• A magnetic field line can never cross another
field line
• Magnetic field lines are defined to begin on the
north pole of a magnet and terminate on the
south pole.
• If magnetic monopoles existed, then magnetic
field lines would begin and end on them.
Field Lines Between Magnets
Unlike
poles
Attraction
N
S
Leave N
and enter S
N
Like poles
N
Repulsion
Electromagnets
Electromagnets
wire
• An electromagnet is formed when a ________
in an electric
iron _____
core producing a
circuit is wrapped around an _____
magnetic field.
• The magnet that results loses its magnetism if the electric
stops ________.
flowing
current ______
electricity
• Electric current is simply the flow of ______________.
(or the flow of charged particles, like electrons)
Generators
mechanical
electrical
• A generator changes ____________ energy into ___________
energy when a coil of wire is rotated near a magnet.
S
N
Simple Electric Motors
mechanical energy by rotating
electrical energy into ____________
A motor changes ___________
poles of a magnet.
an electromagnet between _______
S
N
How it works:
electricity
• The coil of the electromagnet is connected to a source of ___________.
magnetic field
• When electricity flows through the electromagnet, a ___________
is produced.
S
N
S
N
spin
• The rotating coil of wire can be attached
_________ to an object to make it _____.
Examples: wheels
________ on an electric car, fan
___ blades, a ______ ____.
S
N
spin
• The rotating coil of wire can be attached
_________ to an object to make it _____.
disco ball
wheels on an electric car,fan
Examples: ________
___ blades, a ______
____.
S
N