Electricity is one element of physics that we encounter on a daily basis. It powers our televisions and our computers and keeps the lights on at home. Magnets are something we think of as less common, only using them when we need to navigate using a compass or stick something to our fridge. But electricity and magnetism are really just two pieces of the same thing! Let’s shed some light on this idea.
We can see some examples of this relationship using the induction coil. There are really two parts, so lets tackle them one at a time. First, whenever electricity runs through a wire, it creates a magnetic field. If the wire is in a circle, the magnetic field will be the strongest through the middle. By stacking up several loops of wire to make a coil, then we can create an electromagnet.
Diagram of an electromagnet. Credit P. Wormer.
Electromagnet at AstroCamp. Pressing the button sends electricity through the wire solenoid which is coiled around a nail to create a magnetic field.
Not only can electricity be used to create a magnet, but magnetism can be used to create electricity. When a conductor, like a metal wire, feels a changing magnetic field, an electric current is created. We can even use this electricity to power a lightbulb! This process is called induction, and it is the basic principle by which electricity is generated in almost all power plants.
Strong neodymium magnets are rotated inside a coil of copper wire, producing a current. The needle moves back and forth, indicating the the current produced in this way is alternating, or AC current.
Combining both of these ideas, we can now see why the small metal ring hovers. Turning on electricity through the coil of wire creates a magnetic field that is felt by the metal ring. Then, through the process of induction, electricity is created in the ring. The ring is now an electromagnet with electricity running through it! The magnetic field from the ring and from the coil are pointed in opposite directions, so they repel, causing the ring to hover in midair. By submerging the ring in liquid nitrogen, we can lower its resistance and increase the electric current. A stronger current creates a stronger electromagnet and the ring shoots up to the ceiling!