Transcript Magnetic field - Southgate Schools

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It is a substance that contains a magnetic field.
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There are three primary types of magnets;
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Ferromagnetic- A substance that is naturally and
permanently magnetic like iron.
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Paramagnetic- which becomes magnetic under the
influence of a magnetic field.
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Electromagnet- Becomes magnetic under the influence
of an electric current. Is no longer magnetic when
electricity flow is stopped.
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Magnetic field =surrounds a magnet and can
exert magnetic forces.
Magnetic force =the force a magnet exerts on
another magnet, on iron, or a similar metal, or on
moving charges (magnetic force is one aspect of
electromagnetic force)
Fig. 35.1.1. Magnetic field lines – single magnet
Fig. 35.1.2. Magnetic field lines – two magnets
Iron filings lining up along the magnetic field
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A permanent magnet is a substance that
holds a magnetic field indefinitely.
Iron, Cobalt, and Nickel are the only
substances that are naturally magnetic.
But, Co and Ni are somewhat rare, so the vast
majority of magnets are made of iron.
Euro pennies have steel
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An electromagnet starts with a power source and a wire.
Batteries/Electricity produce electrons.
Flowing electrons produce an electric field, which induces a
magnetic field.
Electromagnetic devices are used to change electrical energy
into mechanical energy.
Examples of electromagnetic devices: electric motors,
galvanometers, loud speakers.
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Electromagnets can easily
be made at home with a
copper wire, a nail, and a
battery.
Wrap the wire around the
nail and hook it to the
positive and negative ends
of the battery.
Suddenly the nail is
magnetic and can attract
iron objects.
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A magnetic field in a
current carrying wire can be
increased by wrapping the
wire into a coil. This coil of
wire is called a solenoid
When a magnetic core is
placed in a solenoid, an
electromagnet is formed
This is the basis of many
electric motors.
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The magnetic field is a dipole field. That means
that every magnet MUST have two poles, a positive
(+) or negative (−) electrical charge (a north and a
south pole).
Electrical charges are called monopoles, since they
CAN exist without the opposite charge.
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He discovered the connection
between electricity and magnets
by chance in 1820.
As he prepared for one of his
classes, he noticed that when he
turned on the electric current in a
wire, a compass needle that was
on another experiment changed
its position.
When the electric current was
turned off, the compass needle
returned to its original position.
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This magnetic field forms circles around
a straight wire carrying the current.
Point your thumb in the direction of the
current (which is toward the negative
terminal)
If you curl your fingers around the wire,
the way your fingers curve is in the
direction of the magnetic field.
Strength of magnetic field = magnetic
induction, given the symbol B, measured
in units of Teslas, T derived from
(N/A‧m)
B=F
(T) (Eq. 12)
I∙L
Where B = Magnetic Field (T)
F = Force on Wire (N)
I = Current (A)
L = Length of Wire (m)
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The opposite of an electromagnet is also true also!
When a magnetic field rotates around a wire, it
generates an electric current.
A hand-cranked dynamo charges a battery for an emergency radio…
Or you can have a hamster do it
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Use water or wind to turn
magnets to generate electricity
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Closed-cycle pressurized water turbines
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An electric current
flowing around a rod
will make a magnet.
It is called an
electromagnet
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A moving magnetic
field flowing around a
wire will make
electricity.
It is called a generator
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Electricity and magnetism are both aspects of
A. the north pole.
B. the south pole.
C. electromagnetic force.
D. ferromagnetic material.
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Electricity and magnetism are both aspects of
A. the north pole.
B. the south pole.
C. electromagnetic force.
D. ferromagnetic material.
When electric charges are moving through a
wire, a magnetic field is created. The wires
are made out of materials/metals that can be
magnetized.
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A fan uses a rotating electromagnet to turn
its blades. This is an example of
A. magnetic poles.
B. an electric motor.
C. a galvanometer.
D. a loudspeaker.
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A fan uses a rotating electromagnet to turn
its blades. This is an example of
A. magnetic poles.
B. an electric motor.
C. a galvanometer.
D. a loudspeaker.
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The moving current around the iron core makes
for a giant magnetic field.
This acts much like a magnet flowing around a
wire, creating a strong magnetic field
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The Earth’s magnetic field protects us from harmful
solar particles by deflecting or absorbing them.
The aurora borealis is located at the north pole,
because that is where the energized solar particles
come shooting down into the atmosphere.