If you live in the United States, you probably have a pile of magnets in your wallet.
Yes, you read that right.
Our dollar bills are printed with magnetic inks.
When the US Federal Reserve prints money, they use ink that contains iron oxide which can be magnetized.
Magnetic ink is used as a way to reduce counterfeiting.
Try this experiment to see for yourself!
- US dollar bill
- neodymium magnet
- adult supervision
- With adult supervision, put the magnet on top of the paper money.
- Lift the magnet carefully.
- If the magnet is strong enough, it will lift the paper money, too.
- Hold the magnet over different parts of the bill and see which part is attracted more easily.
- Try different bills, e.g. five dollar bill, twenty dollar bill, hundred dollar bill... if you can get a hold of it. Say it's for a "science experiment" 🙂
Normally, these iron particles are not magnetic. That is why when you pass through an iron gate, you don’t see dollar bills flying out of your pocket and attaching themselves to the gate. The iron particles are only magnetized when another magnet is present, and even then, the magnetic strength is very weak.
In vending machines, scanning technology called Magnetic Ink Character Recognition (MICR) is used to verify the authenticity of the bill and the magnetic pattern on it to determine its denomination. Counterfeit detectors use similar technology to detect fake bills.
If you want to see the iron particles used on the bills, here is a daring experiment putting money into a blender.