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.