Download Magnetism

S-72
Students will investigate the properties of electricity and magnetism?
• What is a magnet?
• What are the two poles called?
Chapter 21
Magnetism
SPS10 Students will investigate the properties of electricity and magnetism.
c.
Investigate applications of magnetism and/or its relationship to the
movement of electrical charge as it relates to
- electromagnets
- simple motors
- permanent magnets
21.1 Magnets and Magnetics
Fields
How do magnetic poles interact?
How can a magnetic field affect a magnet that enters
the field?
Why are some materials magnetic while others are not?
21.1 Magnets and Mag Fields
How do magnetic poles interact?
• Magnetic force – the push or pull a magnet
exerts on
– Another magnet
– On iron or a similar metal
– On moving charges
21.1 Magnets and Mag Fields
How do magnetic poles interact?
• Magnets have two poles
– North and south
– Like poles repel
– Opposite poles attract
21.1 Magnets and Mag Fields
How can a magnetic field affect a magnet that enters the field?
• Magnetic field – an area around a magnet
that will attract or repel other magnets
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–
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Begin at the north pole
End at the south pole
Can be seen using iron dust
Arrows point in the direction of force
on a north pole
– The earth has a magnetic field
21.1 Magnets and Mag Fields
Why are some materials magnetic while others are not?
• Magnetic fields are cause by spinning
electrons
– Most of the time magnets are paired, and the
fields cancel out
– Magnetic domain – a region that has a large
number of electrons with fields in the same
direction
– Magnetized – most of the domains are pointed
in the same direction
S-73
Doin’ The Happy Test Day Dance
S-74
What does an electron do to create a
magnetic field?
What is a domain?
What must happen to the domains in a
substance for it to be a magnet?
21.2 Electromagnetism
How can an electric charge create a magnetic field?
How is an electromagnet controlled?
How does an electric motors work?
21.2 Electromagnetism
How can an electric charge create a magnetic field?
• Electricity and magnetism are two faces of
the electromagnetic force.
– Electric force from
charged particles
– Magnetic force caused
by spinning of charged
particles
21.2 Electromagnetism
How can an electric charge create a magnetic field?
• Magnetic fields are formed by moving
electric charges (Hans Christian Oersted)
– If the charge moves down a wire, the magnetic
field circles the wire
21.2 Electromagnetism
How can an electric charge create a magnetic field?
• Magnetic fields will put a force on a current
carrying wire
– These ideas are used to build
• Electromagnets
• Electric motors
• Electric generators
21.2 Electromagnetism
How is an electromagnet controlled?
• Solenoid – a coil of current carrying wire
that produces a magnetic field
– A ferromagnetic rod inside a
solenoid will increase the field
strength
– This is an electromagnet
21.2 Electromagnetism
How is an electromagnet controlled?
• The strength of an electromagnet can be
controlled by
– Changing the current
– Changing the number of loops
– Changing the type of core
21.2 Electromagnetism
How does an electric motor work?
• Electric motor
– Electricity produces an electromagnet
– The electromagnet is
attracted or repelled by
another magnet
– A commutator ring changes
the poles as after ½ a spin
S-75
What is needed to make an electromagnet
work?
S-76
Using the right hand rule, what is the
direction of the
magnetic field
around a wire if
the current is
traveling
upward?
21.3 Electrical Energy
Generation
How does a generator work?
What are some sources of electrical
energy in the United States?
21.3 Electrical Energy Gen.
How does a generator work?
• Electromagnetic Induction – producing a
current by
– Moving an electrical conductor in a magnetic
field
– As simple as running
a magnet through a
coil
– The faster the movement the higher the current
– Current stops when the motion stops
21.3 Electrical Energy Gen.
How does a generator work?
• Generator – converts mechanical energy to
electrical energy
– Movement to current
– Rotates a coil in a magnetic field
– Power plants
produce AC current
21.3 Electrical Energy Gen.
How does a generator work?
• Generator
Generator Simulation
– Loops of wire are spun
– Whatever runs the power plant spins the wire
– Every half spin the direction
of current changes
– Takes about 3300 watts to
run a house
21.3 Electrical Energy Gen.
What are some sources of electrical energy in the United States?
• Sources of energy in the US
–
–
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49.8%
19.9%
17.9%
6.5%
3%
2.3%
Coal
Nuclear
Natural Gas
Hydroelectric
Petroleum
Wind, Solar, Geothermal, Biomass
S-77
What is electromagnetic induction?
What kind of current does it produce?
S-78
A. What is the direction of the magnetic
field around the wire (arrow points the
direction of the current)
B. Draw the field around the magnet
below.
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S-79
Test Day!
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