These experiments are from Robert Krampf - The Happy Scientist
This week's experiment is the result of a teacher asking for experiments with magnets. If you have ever played with magnets, you know that they attract iron, steel and some other metals. But what about money? To try this, you will need:
a fairly strong magnet
I used US money, but it would be interesting to try money from other countries. Start with a penny. Bring it near a strong magnet (I tested all of the magnets on our refrigerator door and selected the one that would lift the most weight.) Does it stick? No. The composition of US pennies has varied, but they are currently made of zinc and copper, neither of which is attracted to a magnet. In 1943, they were made of steel, so if you are lucky enough to have one of these, it would be attracted to the magnet. It would also be a collector's item, so take good care of it.
Next, try a nickel. It should stick, right? Nickel is a magnetic metal, just like iron. Try it and see what happens. If it is a US nickel, it does not stick. Even though we call them nickels, US nickels do not contain enough nickel metal to make them magnetic. Other countries have coins that will attract a magnet, so if you live outside the US, check carefully.
Keep working your way through the coins. In the US, you will not find any coins that attract a magnet, but don't give up yet. Once you are finished with the coins, it is time to try the bills. Bills? They are made of paper, and anyone that has ever played with magnets knows that they do not attract paper. Still, to be scientific, we should test it. We want the bill to be hanging freely, so that it will be easy to see if it is attracted to the magnet. I accomplished this by closing one corner of the bill in the bottom of the door to our kitchen cabinet. This left the bill hanging down. Bring the magnet close to the bill. Pick a place on the bill that has lots of ink. What happens? It sticks! The bill is actually pulled towards the magnet and sticks! Why?
United States bills are printed with magnetic ink. This magnetic ink is what attracts the magnet. Why is the ink magnetic? It is a way to detect counterfeit bills, helping mechanical bill changers detect fakes. They also use the patterns of magnetic ink to tell if a bill is a $1, $5, $10, etc. That helps prevent people from "making money" with a copy machine. Since they do not print with the special, magnetic ink, the copy would be identified as counterfeit.
If you run into problems, your magnet is probably not strong enough. Avoid
the rubberized, flat magnets, as they are not strong enough. You can get
very powerful, rare earth magnets from Radio Shack and electronic supply
stores. If you still can't get your $100 bills to stick to the magnet, feel
free to send them to me for further testing.
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