Radio conversation between two ships passing in the night...

Voice 1: "We can see your lights and you are on a collision course with our vessel. Please divert your course 15 degrees to the North to avoid a collision."Voice 2: "I can see your lights too and recommend you divert your course 15 degrees to the South to avoid a collision."Voice 1: "This is the captain of a US Navy ship. I say again, divert YOUR course."Voice 2: "No, I say again, you divert YOUR course."Voice 1: "I am in the U.S.S. Wolverine, the largest battleship on this ocean. I DEMAND that you change your course one-five degrees North!"Voice 2: "I am in the Point Amour lighthouse. Your call, sir."

Magnetism MagnetismI. Characteristics of Magnets

(p.624-627) Magnetism Magnetic poles Magnetic field Magnetic domain

What are magnets?Magnets are metal objects that create

magnetic fields and attract other objects containing iron, nickel or cobalt.

Properties of Magnets

Attract iron, nickel and cobaltHave magnetic polesExert magnetic forcesSurrounded by a magnetic field

what else do we know that is surrounded by a field??

A. MagnetismMagnetism

force of attraction or repulsion between unlike or like poles

due to the arrangement of electrons

closely related to electricity

The SI unit is tesla (T)

Magnetic Poles

The strongest force on a magnet is found at the ends of the magnet

The ends of the magnet are called the Poles If you tie a string to a magnet, the part that is

the “north” always points to the north pole of the Earth.

There are North and South poles on ALL magnets.

B. Magnetic PolesMagnetic Poles

like poles repel

unlike poles attract

a broken magnet creates new poles

Magnetic ForcesThis is the push or pull a magnet causes. If two poles are the same they _______

If two poles are opposite they _______ What have we talked about that also has

forces that work this way?

Magnetic FieldThe region around a magnet in which

magnetic forces can act or are effective.The magnetic field is strongest around the

poles!

C. Magnetic FieldMagnetic Field

area around a magnet where magnetic forces act

field lines show direction of field (NS)

D. Magnetic DomainMagnetic Domain

groups of atoms with aligned magnetic poles

in a magnetized object, domains are all aligned

domain

All materials are not magnetic The atoms in matter cause magnetism

All atoms have a north and south pole created by the movement of electrons.

In most substances the atoms are arranged such that the magnetic fields are canceled.

In other matter, like iron, nickel and cobalt, the atoms group together in regions called domains. These domains can become aligned. If most of the domains are aligned, the object becomes magnetic.

Objects containing iron, nickel or cobalt can be magnetized by aligning the domains.Magnets can lose magnetic properties if these atoms lose alignment

By striking or dropping a magnet too hard By heating a magnet to high temperatures

You cannot have half a magnet.

Types of Magnets Ferromagnets

Natural magnets made of iron, cobalt or nickel

Electromagnets Usually with an iron core and made by an electric current

Permanent Difficult to magnetize but retain properties

Temporary Easy to magnetize but lose properties easily

Earth as a MagnetThe Earth acts as if it has a bar magnet

running through it!The geographic North Pole is the magnetic

South Pole.The Earth’s geographic

poles are on the axis

around which Earth spins.The spinning of Earth’s

iron and nickel core causes alignment of electrons, thus the magnetic field.

AuroraThe Aurora Borialis and Aurora Australis are

“light shows” that are caused by charged particles from the sun interacting with our upper atmosphere. These are usually visible in the far north and south because this is where the magnetic field is dipping back into the earth.

Recap!!1) What are 4 magnetic properties?2) How do magnetic forces interact?3) Why are some materials magnets while

others are not?

Magnetism MagnetismIII. Producing Electric Current

(p.633-639) Electromagnetic Induction Electric Generator DC & AC Transformer

Introduction to Magnetism from Electricity

Ever heard of Maglev??

Discovery of Electromagnetism

Discovered by a man named Hans Oersted.

His research concluded that an electric current produces a magnetic field in the direction of a given current

Electromagnetism is the interaction between electricity and magnetism.

A. Electromagnetic InductionElectromagnetic Induction

producing a current by moving a wire through a magnetic field

some microphones work just like mini-speakers in reverse

sound waves cause coil to move current

Dynamic Microphone

Coil

B. Electric GeneratorElectric Generator

mechanical energy electrical energy

armature is rotated between magnet poles

magnetic field induces a current in the wire coil

MOTORGENERATOR

B. Electric Generator Hydroelectric Dam

PE of lake water is converted to KE

mechanical KE turns the generator shaft which creates electrical energy

C. DC & ACDirect Current (DC)

current flows in one direction dry cells

Alternating Current (AC) current reverses its direction

at regular intervals electrical outlets

D. TransformerTransformer

increases or decreases AC voltage primary coil AC produces a magnetic field that

induces AC in the secondary coil voltage ratio = ratio of turns in each coil

D. TransformerStep-up Transformer

increases the voltage more turns power plants

Step-down Transformer decreases the voltage fewer turns household appliances

(hairdryers, etc.)

Magnetism MagnetismII. Uses of Magnetic Fields

(p.628-632) Electromagnet Speaker Motor

ElectromagnetElectromagnet

strong, temporary magnet formed when current is passed through a coil of wire surrounding an iron core

acts like a bar magnet when current is on

SpeakerSpeaker

electrical energy mechanical energy

wire coil moves back & forth as its magnetic field interacts with the field of a fixed magnet

forced vibration causes the cone to move sound

Video

MotorMotor

electrical energy mechanical energy

electromagnet rotates between the poles of a fixed magnet

commutator reverses the poles of the e’magnet

Motor

brushes & wires to battery field magnet

armature & commutatorassembled motor