Magnetism

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# Magnetism - PowerPoint PPT Presentation

Magnetism. Students will describe the properties of magnets and demonstrate their fields. Properties of Magnets. Magnets have two poles – north and south The magnetic force is strongest at the ends of a magnet which are called poles They exert a magnetic force. Magnetic Force.

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Presentation Transcript

### Magnetism

Students will describe the properties of magnets and demonstrate their fields.

Properties of Magnets
• Magnets have two poles – north and south
• The magnetic force is strongest at the ends of a magnet which are called poles
• They exert a magnetic force
Magnetic Force
• North attracts south
• South repels south, and north repels north
Strength of Magnetic Force
• The closer two magnets, the stronger the force.
• The further two magnets are, the weaker the force becomes.
• This is very similar to the gravitational force between two masses
Magnetic Fields
• A magnetic field exists in the region around a magnet
• The shape of the field reflects the shape of the magnet, as you will learn in the lab today
• You will draw the field around each magnet that you test
What makes materials magnetic?
• Some materials are magnetic, some are not
• The atoms of some materials cancel out the magnetic charge resulting in an inability to magnetize.

continued…

With atoms in other materials, the electrons clump on one side creating a polar molecule. One end is negatively charged and one is more positively charged.
• The atoms line up, negative side attracting the next atom’s positve side
• This creates a positive end and negative end in the material.
Can magnets loose their force?
• Dropping or hitting a magnet will weaken the magnet, or even break it.
• High temperatures will also demagnetize.
Can you make a magnet?
• You can temporarily magnetize certain materials
• The atoms in those materials will align north and south for a short time
• In the lab today, make a magnetic chain of paper clips (without twisting them together) and see how long you can make it. Ends linking ends.
The Earth as a Magnet
• What do you recall about the earth as a magnet?
• Where are the ends of the “earth” pretend magnet?
• What are they called?
Three Properties of Magnets
• All magnets have two poles
• They exert a magnetic force
• They are surrounded by a magnetic field
What pole does a compass really point to?

A magnet’s _____ pole

a) South b) North c) center

How Temporary Magnets are different from Permanent Magnets
• Temporary magnets are easy to magnetize, but lose their magnetization easily
• Permanent magnets are difficult to magnetize, but retain their magnetic properties for a long time
What is a Solenoid
• A solenoid is a coil of wire that produces a magnetic field when carrying an electric current
• Attach a wire to a battery that has coils, and it will create a magnetic field! See page 463 in your books!
More on Solenoids
• An iron core creates a stronger magnetic field
• The more coils, the stronger the magnetic field
• The more amperage, the stronger the magnetic field
Question page 477
• On Question 17, it shows four solenoids.
• At your tables, discuss each one and rank them in order of strength.