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The earth is a giant magnetMagnetic field lines

of forceleave the north poleand enterthe south pole Whatis a magnetic field?

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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.

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Magnetic flux patterns

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Magnetic?

These materials along

with certain other alloys arecalled ferromagnetic materials.

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Hard or soft material?

Iron has stronger inducedmagnetism.

Steel has a weaker induced

magnetism.

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Hard or soft?

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Hard or soft?

Iron is a magnetically soft material.

Strong but temporary!

Steel is a magnetically hard material.

Weak but permanent!

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Induced magnetism

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Making magnetsDouble touch method

The end where the stroking pole

leaves the bar

becomes the opposite pole.

M ki t

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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.

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The Domain Theory of magnets

Magnetic material

In demagnetized

condition

Magnetic material

In magnetized

condition

Dipoles inmagnetic

domains

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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.

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Magnetic keepers

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Magnetic effect of current

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Direction of the magnetic field

Grip the wire with your right hand,the field lines will go in the direction

of the fingers.

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Magnetic effect of an electric current

Magnetic flux pattern due to a current

in a long straight wire,

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Magnetic flux pattern due to a current

in a short circular coil of wire.

Magnetic effect of an electric current

Use the right

hand grip rule

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Magnetic effect of an electric current

Magnetic flux

pattern due to acurrent in a

solenoid.

Grip the solenoidwith the right hand

with the fingers in

the directionof the current

The thumb points

to the north pole

Di ti f th ti fi ld

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Direction of the magnetic field

Grip the wire with your right hand,the field lines will go in the direction

of the fingers.

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Kicking wire experiment

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Force on conductor

Field due to

permanent

magnet

Field due to

current

in wire

Two fields interact

to produce

force (motion)

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Flemings left hand rule

Used to determine

direction of motion of conductor

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d.c. electric motor

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Fields interact, coil turns

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END OF MOTORSFOR NOW

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remember

u can not sleep if u dont know it.

sweet dreams