If you live in the United States, you probably carry a stash of magnets in your wallet without even realizing it.
That’s because the US dollar bills are printed using magnetic inks that contain iron oxide, which can be magnetized.
Magnetic ink is used as a countermeasure against counterfeiting. By embedding magnetic properties in ink, the US Federal Reserve has created a sophisticated security feature that makes it hard for counterfeiters to produce fake currency.
The US currency notes come in various denominations, and each money note features a unique design on its face, which gives it a distinct magnetic signature.
If you want to try this experiment for yourself, all you need is a magnet.
And as with any experiments involving magnets, be aware of the danger.Warning: Magnets are very hazardous if swallowed. Please keep them away from children who still put everything into their mouths.
- 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.