Your refrigerator door may be decorated with dozens of colourful magnets, but your home contains other kinds of magnets about which you might not know. Some of them are permanent, made of magnetised metal, and others become magnetic only when they use electricity. The attractive and repulsive forces magnets produce make them useful for motors, speakers, latches and data storage devices. Some of the magnets in your home are plainly visible, others are hidden inside appliances.
The speakers in your stereo contain magnets. The speaker consists of a stationary magnet in a metal frame, a paper diaphragm and a wire coil moulded into the diaphragm's centre. When an electric current flows through the coil, magnetic forces between the coil and the stationary magnet make the diaphragm vibrate in and out. The vibration produces the music you hear. Almost every kind of speaker has a magnet, from tiny earbuds to large loudspeakers.
Your vacuum cleaner has an electric motor that runs by magnetism. Inside the motor, wire coils produce repulsive forces when electric current flows through them. The forces make the motor spin. Unlike refrigerator magnets, which use no power, the magnetic coils in the motor have no magnetism when the vacuum cleaner is turned off. The coils have much stronger magnetism than kitchen magnets.
The doors to many medicine cabinets have a magnetic latch. A magnetic latch consists simply of a permanent magnet in the cabinet and a metal piece on the door. The magnet has just enough force to hold the door shut and opens easily when you need something inside. The magnetic refrigerator door seal replaced mechanical door latch mechanisms in the late 1950s as a safety measure, according to an article on The Straight Dope website.
Many building toys have magnets in them. The magnets make the building blocks stick together. You'll also see magnet couplers used to connect the cars in a toy train set. Magnetic chess and draughts sets keep the game organised with a little magnet in each game piece. By themselves, magnets make fascinating toys and clearly demonstrate magnetic principles.
The credit cards in your wallet all have a dark magnetic strip on the back. The strip contains data codes including the account number and your name. When you swipe the card at a store, an electronic device in the reader senses the magnetic codes and converts them into readable words and numbers.
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