Magnetism

What is magnetism?

Force of attraction or repulsion due to electron arrangementMagnetic forces are the strongest at the polesMagnets have two poles: North and South

Magnetic poles and fields

Magnets always have two polesIf a magnet is cut it will still have two polesLike magnetic poles repel Unlike magnetic poles attractA magnetic field is the area in which magnetic forces act

Questions

What two forces are involved in magnetism?Which subatomic particle accounts for magnetism?Explain the interaction between magnetic poles when they are close together.

Magnetic materials

Natural magnets have naturally occurring magnetic properties ex: LODESTONE (magnetite)

Temporary magnets

Easy to magnetize

Lose their magnetism quickly

Ex: Soft iron

Permanent magnets

Hard to magnetize

Stay magnetized longer than temporary magnets

Ex: alnico (cobalt, nickel, aluminum)

Questions

How is a temporary magnet different from a permanent magnet?

Give an example of a natural magnet.

Earth’s magnetic properties

Gilbert was a scientist that showed that the Earth behaves as a magnet

The Earth’s magnetic field is strongest at the poles

Earth’s magnetic field is called the magnetosphere

Compasses

Compasses are used to determine directionCompass needles are magnetized and respond to the magnetic field of the EarthCompasses point to the MAGNETIC POLES OF THE EARTH

Other sources of magnetism

Magnetic fields of the Earth and other planets are related to their cores

The sun is a source of a magnetic field

Questions

Which scientist described the Earth’s magnetic properties?

Name the devices used to indicate geographic direction based on the Earth’s magnetic field.

Questions

What is the name of the Earth’s magnetic field?

Where is the Earth’s magnetic field the strongest?

Magnetic variation

Magnetic poles of the Earth are different from the geographic poles of the Earth

Magnetic Induction

Process by which materials can be magnetized

What affects magnetic properties?

Spinning electrons cause some metals to have magnetic properties

Magnetic domains are groups of arranged magnetic fields

Dropping,hammering or heating a magnet will cause a magnet to lose magnetic properties

Electricity and Magnetism Electric forces hold atoms and

molecules together. Electricity controls our thinking, feeling,

muscles and metabolic processes. Electricity and magnetism underpin

much of our current technology (e.g. computers).

Electricity and magnetism are linked on a fundamental level.

Electromagnetism

Discovered by Oersted (scientist)

Relationship between electricity and magnetism

ElectromagnetsTemporary magnetsMagnetism can be turned on and offMade by wrapping wire around a piece of iron and sending a current through the wireMagnetic field is in the same direction as the electric current

Increasing the strength of electromagnets

Increasing the voltage or current

Increasing the number of loops of wire

QuestionsExplain magnetic variation.

What is electromagnetism?

Who discovered electromagnetism?

Name two ways to increase the strength of an electromagnet.

What type of magnet is an electromagnet?

Electric motors vs. generators

Electric motors convert electricity to mechanical energy in order to do workGenerators convert mechanical energy to electrical energy

TransformersUsed to increase or decrease voltage

Made of primary and secondary coils

Two types of transformers:

“Step-up” (increase voltage)

“Step-down”(decrease voltage)

QuestionsHow is a generator different from an electric motor?Name two types of transformers.How is a step-up transformer different from a step down transformer?What are the two parts of a transformer?