How are magnets used in credit cards?

The strip on the back of your credit card is made up of magnetic particles that contain the account information. Any contact with a magnet or magnetic field can cause the strip to become demagnetized and the card to be ruined. Exposure to magnets can cause the particles in the strip to rearrange, making the card unreadable.

Read more: Why Do Magnets Ruin Credit Cards? | eHow.com http://www.ehow.com/about_5365431_do-magnets-ruin-credit-cards.html#ixzz1Odckj7cS