• What is a magnet?• What are the two poles called?

S-72Students will investigate the properties of electricity and 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

Chapter 21

Magnetism

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 Magnetics Fields

• 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 FieldsHow do magnetic poles interact?

• Magnets have two poles – North and south– Like poles repel– Opposite poles attract

21.1 Magnets and Mag FieldsHow do magnetic poles interact?

• Magnetic field – an area around a magnet that will attract or repel other magnets – 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 FieldsHow can a magnetic field affect a magnet that enters the field?

• 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

21.1 Magnets and Mag FieldsWhy are some materials magnetic while others are not?

Doin’ The Happy Test Day Dance

S-73

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?

S-74

How can an electric charge create a magnetic field?How is an electromagnet controlled?How does an electric motors work?

21.2 Electromagnetism

• 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 ElectromagnetismHow 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 ElectromagnetismHow 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 ElectromagnetismHow can an electric charge create a magnetic field?

• 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 ElectromagnetismHow 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 ElectromagnetismHow is an electromagnet controlled?

• Electric motor– Electricity produces an electromagnet– The electromagnet is

attracted or repelled byanother magnet

– A commutator ring changesthe poles as after ½ a spin

21.2 ElectromagnetismHow does an electric motor work?

What is needed to make an electromagnet work?

S-75

Using the right hand rule, what is the direction of the

magnetic field around a wire if the current is traveling upward?

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How does a generator work?What are some sources of electrical energy in the United States?

21.3 Electrical Energy Generation

• 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 – 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.How does a generator work?

Generator Simulation

• Sources of energy in the US – 49.8% Coal– 19.9% Nuclear– 17.9% Natural Gas– 6.5%Hydroelectric– 3% Petroleum– 2.3%Wind, Solar, Geothermal, Biomass

21.3 Electrical Energy Gen.What are some sources of electrical energy in the United States?

What is electromagnetic induction?

What kind of current does it produce?

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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.

S-78

N S

Test Day!Happy, Happy!

Merry, Merry!

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