Post on 03-Jun-2018
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William Gilbert, an Englishphysician, first proposed in 1600that the earth itself is a magnet,and he predicted that the Earthwould be found to have magneticpoles.
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Magnets are Useful
They help make work easier. You
can find magnets in the lab, injewelry, for fishing, on the
construction site, in the kitchen, in
cars, radios, video recorders, andeven on the farm.
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Magnet Safety
Safety Note: Keep magnets away from
electronic devices such as computers,
watches, and clocks, as they can damagethese items even with brief contact.
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An unmagnetized substance
looks like
this
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While a magnetized substance looks
like this
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The ends of a magnet are where
the magnetic effect is the
strongest. These are called
poles. Each magnet has
2 poles 1 north, 1 south.
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Like poles repels !
Opposites attract!
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Poles of amagnet alwaysCome in pairs
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How to break a magnet:
1. Drop it
2. Heat itThis causes the domainsto become random again
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If you cut a magnet in half,
you get 2 magnets
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North Poles Cannot Be Separated from South
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Magnetic Fields
The region where the magnetic forcesct is c lled the m gnetic field
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What does a magnetic field look like?
Well, we cant see it for a start, but...
Small particles of iron filings are pushed into
patterns by a magnetic field. If we sprinkle iron
filingson a piece of paper over a magnet we can
see...
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Sprinkle iron filings around a magnet,then you will be able to see the magnetic field.
Place white card over the magnet
and Sprinkle iron filings on a card.
Tap the card gently with a pencil and observe the pattern.
Bar Magnet
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What does a magnetic field look like?
The lines of force are very
close together here the field
is very strong.
The lines of force are further
apart here the field is weaker.
A line of force links one pole of a magnet to the other pole.
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Magnetic field of
Horseshoes magnet
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Magnetic field ofBar magnet
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The pattern and thedirection of a magnetic field can be
mapped using plotting compass.
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Compasses are place around the bar magnet
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The compass needles show the direction of force inMagnetic field.
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lets see how you
doing so far
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The Earth is a magnet:Magnetic South Pole
Magnetic North Pole
It exerts magnetic forces
and is surrounded by a
magnetic field that isstrongest near the
North and South
magnetic poles
Geographic North Pole
Geographic South Pole
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We use the Earths magnetic field to find direction.
The needle of a compass always points toward the
magnetic south pole.
We call this direction North (remember, opposites attract)
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The sun has a magnetic field, too.
It extends far above the suns
surface.
Other planets in the solar
system also have these
magnetic fields
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