Wednesday, 28 January 2015

Electromagnets

It’s simple to make a small electromagnet of your own. All you need is a battery and some wire, and a compass to show the magnetic pull.



Take an ordinary AA or D battery and connect a piece of wire to run from the plus (+) side to the negative (-) side. Place the compass near the wire. You should see that the needle moves away from North, and points in the direction of the wire. This is a sign that the wire is magnetized. Don’t leave your wire connected for more than a minute, because the battery will drain very quickly. As soon as you take the wire off one end of the battery, the compass needle will return to normal.

You can make a much stronger electromagnet by twisting the wire around a pencil a number of times. It should now be able to pick up a paperclip. You can experiment with more twists, or winding the wire around a metal nail. Have fun!

Did You Know?

You can take the magnetism out of a magnet by hitting it soundly with a hammer.The vibrations you cause when you strike the magnet will shake up the magnet's atoms and knock the domains out of alignment, so it will no longer be magnetic. To remagnetize it, you'd have to put it in touch with a magnetic field.


Before the invention of the compass, people used a bowl and spoon to navigate. The Chinese were probably the first to recognize the direction-finding ability of magnets. In A.D. 83, during the Han dynasty, magnetic lodestone was carved into a bowl and spoon. The spoon was free to orient itself within the bowl to the direction of Earth's magnetic field, always pointing in the same direction.


Magnetism helps keep our currency free of counterfeit money. The ink that's used to print bank checks and paper money is treated with magnetic dust so that it can be distinguished from ink used in counterfeit currency. Vending machines and coin sorters also use magnetism to identify slugs, or metal disks.


Some lobsters use a built-in compass to migrate each fall. Spiny lobsters have tiny bits of magnetite-the same material that's in lodestones-in their brains. In late autumn, the lobsters detect the Earth's magnetic field and use their internal compass to travel through the dark of night and huge waves. Every year, without fail, they successfully find their way to warmer water before the chilly winter arrives.

Magnets and Springs

Why don't you play this game to practise using magnets?




Click on the image to find some experiments using magnetism



edubloggers

edubloggers

Recursos TIC

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