Standard
Investigate and explain that electric currents and magnets can exert a force on each other. (S8P5c)
Big Idea #1
Magnets can exert a force on an object at a distance.
Big Idea #2
Currents produce magnetism and magnetism can produce currents.
Magnets and Magnetism
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| (c) M. Prince, 2013 |
Do you remember the definition of a force as described in our energy unit? Did you say a PUSH or PULL? I knew I could count on you to remember. Magnets are composed of two poles and a magnetic field, in which the field lines extend from the North pole towards the South pole. The further away from the magnet, the weaker the force applied to an object. Think about it: How close does a magnet need to be to another magnetic material before it pulls or pushes that object away? Why does a magnet push or pull objects? To answer these questions we will need to look at two magnets. When you place to like poles close to one another, each exerts a force onto the other. They REPEL or push away from one another. On the other hand, when you have two opposite poles close to one another, each one pulls the other closer to it so that they become connected. In this case, they are ATTRACTED to one another.
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| (c) M. Prince, 2013 |
Does this mean that this can happen with all objects? Well for this we need to see why some materials are magnetic and why others are not. First let's start with magnetic materials.
The magnetic fields of the atoms in magnetic items are aligned. In other words the magnetic field of atoms in the same magnetic domain point in the same direction. Each magnetic domain (group of atoms) can point in different directions, but once they are close enough to a magnet the domains become aligned. The more domains that align result in a stronger magnetization of the material.
The magnetic fields of atoms in nonmagnetic items are weak and and are not aligned. As a result, these materials are unable to show any signs of being magnetized. An example of this would be a piece of chalk. You can move a magnet closer and closer to the chalk and it will never become magnetized.
In a magnet, ALL of the magnetic fields of the atoms are pointing in the same.
So let's recap:
Nonmagnetic materials have magnetic fields moving in all directions canceling one another out and keeping the material from being magnetized.
Magnetic materials have magnetic fields that point in the same direction within each magnetic domain. These objects can be pulled by magnets.
Magnets have magnetic fields that all point in the same direction from one domain to the next allowing them to be magnetized.
The Earth: A Big Magnet
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| (c) M. Prince, 2013 |
How cool is this image? The Earth is really just a big magnet! How is the Earth similar to the bar magnet? How is the Earth's magnetic field formed? How does it change over time? How does the magnetic field protect the Earth? Use these two videos to answer these questions.
Video #1
Video #2
Magnets and Health
Some people believe that magnets have healing powers. Why is this so? What do you think according to the research?
The Healing Powers of Magnets
Controlling Chronic Pain with Magnetic Therapy
Can Magnets Cure Pain?
Magnets Producing Currents
Problem Question: Can a Magnet Produce and Electric Current?
Research: Magnets can produce current. [PDF Printable]
You can build a generator at home with these lab instructions to discover the answer.
Currents Producing Magnetism
Problem Question: Can an Electric Current Produce Magnetism?
Research: Current can produce magnetism. [PDF Printable]
