Gadgets that rely on magnetic levitation, also known as magnetic hovering, to suspend various objects in the air are not hard to find these days, but how do they work? Why is it not possible to suspend one magnet over another without the top magnet inevitably making contact with the bottom magnet? The answer is … science!
A Gentle Introduction to Magnetism
As you know, ferrite magnets (composed of ferric oxide combined chemically with one or more additional metallic elements) and neodymium magnets (made from an alloy of neodymium, iron, and boron) are useful for much more things than securing important documents and notes to your whiteboard.
Being permanent magnets, ferrite magnets and neodymium magnets have two magnetic poles: one South pole and one North pole. The names of the two poles come from a time before Google Maps and GPS navigation, when compasses provided the most reliable method for finding the right way to a destination.
Both the South pole as well as the North pole create magnetic fields, which typically manifest as either a force that attracts or repels other magnets, depending on their polarity. The same magnetic polarities create a repulsive force while opposing magnetic polarities create an attraction force.
Magnetic Levitation at Home
If you have two magnets of roughly the same size, you can try a little experiment with magnetic levitation.
Place one magnet on a solid surface and position another magnet directly above it so that the magnets are facing each other with the same poles. If you hold the top magnet, you should feel the repulsive force counteracting the weight force. Notice that as soon as you let go of the top magnet, it falls after being suspended in the air only for a couple of milliseconds.
Does this little experiment prove that floating magnets are a scam? Far from it! It demonstrates the problem described in Earnshaw’s theorem, which states that it is not possible to achieve static levitation using any combination of fixed magnets and electric charges.
Magic or Engineering?
But if it’s not possible to create a floating magnet using any combination of fixed magnets and electric charges, how come there are so many products, such as this magnetic levitation floating globe with LED lights, that can keep an object suspended in the air? Are they magical? Is sorcery the answer to magnetic suspension?
The answer is: no. Instead of magic, the key to magnetic suspension is, perhaps disappointingly, electricity.
Unlike permanent magnets, electromagnets, in which the magnetic field is produced by an electric current, don’t have a static magnetic field. The magnetic field can be turned on and off with a press of a button as it disappears when the current is gone.
“If you can detect the position of an object in space and feed it into a control system that can vary the strength of electromagnets that are acting on the object, it is not difficult to keep it levitated. You just have to program the system to weaken the strength of the magnet whenever the object approaches it and strengthen when it moves away,” explain Philip Gibbs and Andre Geim in their famous publication on electromagnetic levitation.
To detect the exact position of the levitated object, manufacturers of levitating gadgets, including FOXNOVO, the company behind this levitating speaker, use a Hall effect sensor, which is a transducer that varies its output voltage in response to a magnetic field. As the object is moving up and down, the hall sensor outputs variables which represent the current distance between sensor and object, and the electromagnet responds appropriately, as instructed by a microcontroller.
As magical as magnetic levitation may seem, this eye-catching method of suspending an object in the air without any support relies on the magnetic force to counteract the effects of gravity. And unlike with magic tricks, understanding how magnetic levitation works only makes the gadgets that use it more interesting.