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

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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.

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