Magnetic stirrers use a motor to rotate an internal magnet very quickly, which attracts and pulls a metal stir stick into a circular motion to stir a liquid. Some stirrers use stationary electromagnets instead of a magnet on a motor.
Magnetic stirrers are commonly used in chemistry labs to stir liquids quickly and effectively. They consist of a motor, magnet or electromagnet and a metal stir stick which is sometimes called a flea. Different fleas can be different sizes and have different coatings. The fleas are easily cleaned and will not result in contamination of the solution.
Magnetic stirrers are used because they are very efficient and quiet. They are safe to use for solutions in glass containers and do not have external moving parts. They also can be used within a closed system because they can be turned on and off wirelessly.
Many magnetic stirrers also include a hot pad that heats up the solution. This allows for super-saturation of liquids, which means that the solution is heated up to allow it to hold more solute. The magnetic stirrers with hot plates often have a built-in thermometer to allow for close monitoring of the solution that is being stirred.