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Advanced Physical Science
Magnetism
Magnetism: The ability of some substances to attract iron, steel, and some other metals
Magnetism is a property of moving e- Every moving e- has a magnetic field around it Each e- in every atom is a tiny magnet
Magnetic Domain
Electrons are negatively charge particles that move around the nucleus of atoms
Moving electrons produce magnetic fields that give atoms a N and S pole
In most materials (like Copper and Aluminum) magnetic fields cancel each other out. Result: the object is not magnetic
Magnetic Domain (cont) In some materials (like iron, nickel and
cobalt), the atoms group together in tiny regions called domains.
Domains are like tiny magnets of different sizes within an object.
Magnetic Poles
Like poles repel
Unlike poles attract
Broken magnets create new poles
Magnetic Field Area around a magnet where magnetic
forces act Forces are in a specific direction shown by
field lines The lines map the strength of the magnetic
field (stronger at poles)
Iron filings placed around a magnet will show the shape of the magnetic field around the magnet
Permanent Magnets Made from magnetic material (an alloy
of aluminum, nickel, and colbalt) and have a persistent magnetic field
Retain magnetic properties better than other materials
A strong current is used to align the domains of the alloy
Once the domains are lined up, they tend to remain that way
Making a Magnet
A magnet can be made by aligning domains in an object
Example: An iron nail can be magnetized if you rub it in one direction with one pole on a magnet
The magnetic field of the magnet will cause the domains in the nail to rotate and align with the magnet
Losing Magnetism
Magnets can lose magnetism if domains of a magnets become unaligned
Things that cause magnet to get out of alignment:Dropping a magnetHeating a magnet
Magnetism from Electricity An electric current will produce a
magnetic field Electromagnetism: The interaction
between electricity and magnetism
Magnetism from Electricity: Solenoids A coil of wire that produces a magnetic field
when carrying an electric current Increase strength of magnetic field produced
by solenoid by…Adding more loopsIncreasing the current
in the wire
Magnetism from Electricity: Electromagnets Temporary magnet formed by placing iron
inside a current carrying wire (electricity) Magnetic field is only present when current
is flowing Strength of magnetic field is increased by
adding more turns of the wire or by increasing the amount of current through the wire.
Magnetic properties can be controlled by changing the current.
Examples of Electromagnets
Maglev Train, Japan
Electromagnet in a salvage yard, turned on and off to lift scrap metal
Press the doorbell, switch in solenoid circuit closes, electric current created, iron rod is pulled through solenoid, rod strikes bell
Electricity from Magnetism: Electromagnetic Induction
Magnetic Field can produce an electric field
The size of electric current depends…Number of wire
loopsHow fast move
magnet The direction
depends onWhether magnet is
pulled or pushed
Electricity from Magnetism (cont) In previous example,
electric current induced by moving the magnet
Electric current can also be induced by moving the wire
Application of Electromagnetic Induction: Generator Converts MECHANICAL ENERGY to ELECTRICAL ENERGY
A generator rotates a coil of wire through a magnetic field The changing magnetic field around the wire induces
electric current in the wire The electric current produced
by a generator changes
direction each time the
coil makes a ½ turn
ALTERNATING
CURRENT (AC)
http://www.generatorguide.net/howgeneratorworks.html
Transformer Increases or decreases the voltage of an
alternating current Consists of 2 coils wrapped around an iron ring Step-up transformer: Increases voltage Step-down transformer: Decreases voltage
Electrical Energy to your Home Generator at the power plant produces
electric current with HIGH voltage Step-up transformers increase the
voltage in order to decrease loss of POWER that occurs during transmission over long distance
Step-down transformers decrease the voltage before the electric current reaches consumers
How Electricity Gets to Your House Electricity is made at a power plant by huge
generators (HIGH voltage) Most power plants use coal, but some use natural gas, water or even wind.
The current is sent through transformers to INCREASE THE VOLTAGE to push the power long distances.
The electrical charge goes through high-voltage transmission lines that stretch across the country.
It reaches a substation, where the VOLTAGE IS LOWERED so it can be sent on smaller power lines
How Electricity Gets to your House (cont.)
It travels through distribution lines to your neighborhood, where smaller pole-top transformers reduce the voltage again to take the power safe to use in our homes.
It connects to your house through the service drop and passes through a meter that measures how much our family uses.
The electricity goes to the service panel in your basement or garage, where breakers or fuses protect the wires inside your house from being overloaded.
The electricity travels through wires inside the walls to the outlets and switches all over your house.
FYI…Nuclear Power Plant
Thermal Energy from a nuclear reaction boils water to produce steam
The steam turns a turbine The turbine turns the magnet of the
generator, inducing electric current and generation electrical energy.