# Electromagnets

There is a very interesting type of magnet called electromagnet. It is a device in which electricity runs through a wire wrapped around a piece of iron and behaves like a magnet.

You can build an electromagnet at home: An electromagnet starts with a battery or battery (or some other power source) and a wire. What the cell produces are the electrons.

If you look at any battery D (a flashlight battery, for example), you can see that there are two ends, one marked with a plus sign (+) and one marked with a minus sign (-). The electrons are grouped at the negative end of the cell and can flow to the positive end with the aid of a wire. If you connect a wire directly between the positive and negative terminals of a stack, three things will happen:

1. electrons will flow from the negative side of the cell to the positive side as fast as they can;
2. the battery will discharge very quickly (in a matter of minutes). For this reason, it is not usually a good idea to connect the 2 terminals of a battery directly to each other, usually, you connect some kind of charge in the middle of the wire. This charge can be a motor, a lamp, a radio;
3. A small magnetic field is generated in the wire. It is this small magnetic field that is the basis of an electromagnet.

### Mess magnet information

Why are credit cards demagnetized when they are near television sets?

Attention to the places where you leave the wallet!

Various appliances, such as a TV, stereo, and cell phone, can damage credit cards. The customer information is magnetically recorded, and any magnet can interfere with that recording. "A connected TV produces a magnetic field that messes up the information recorded on cards, videotapes, computer diskettes or even subway tickets, which work on the same principle."

The technique of recording was born in Denmark at the end of the last century, when engineer Valdemar Poulsen demonstrated that a magnetized piano string could hold the human voice. The invention, named telegraph, won a prize at the 1900 Paris exhibition, but was not commercially successful. By contrast, the method developed by Poulsen has been refined and is now used to store any type of information - from computer-typed text to your bank password.

1. The magnetic stripe is covered with a layer of iron oxide particles.

2. To record any password, you need to pass an electromagnet over it. This causes the particles to turn into small magnets, which are aligned, encoding the data.

3. If there is another magnetic field nearby, such as a TV or a speaker, the stripe's aligned magnets are attracted again and lose their way. The information goes out.