Do you know what an electromagnet is?
Boy did you come to the right place and ask the right question. Jefferson Lab is magnet central to the world. Several of the world's most skilled magnet designers work here. Magnets are used extensively in high energy and nuclear physics. We use some of the most powerful magnets in the world and certainly some of the coldest.
Ok, to answer your question. Yes, I know what an electromagnet is.
I have to assume you want to know a little more than that.
An electromagnet is a magnet that is created when electricity flows through a conductor. The magnetic field goes around the conductor. The typical way electromagnets are built is to wrap many coils of wire around a ferromagnetic core (almost always iron). Ferromagnetic materials, such as iron, nickel or cobalt have the property of concentrating magnetic fields through them, making the field strength higher than without the core. When electricity passes through the coils of wire, a magnetic field develops around it, which is caught in the ferromagnetic core. The magnetic field goes through the core, out one end of the core and back in the other end.
Here at Jefferson Lab we have tons of magnets, literally. We use electromagnets to steer, position, and shape the electron beam we use for our experimental physics program. The really cool magnets here are the spectrometer magnets used in our experiments. These magnets are used to analyze the momentum of particles passing through them. The speeding particles are shot through the magnetic field. The paths of particles with low momenta get bent a lot. The paths of particles with high momenta do not get bent as much. To make these magnets very powerful, but to not use much electricity, the conductors used are superconductors. These are materials that when cooled to a few degrees above absolute zero (the temperature at which matter has no energy, the lowest possible temperature (near -273° Celsius, -460° Fahrenheit)) lose all resistance to the flow of electricity. These magnets can have magnetic fields up to 40,000 times the strength of the earth's magnetic field! Some of these magnets can be as large as a house and weigh hundreds of tons.
Electromagnets are used everywhere. Electric motors, speakers, and power door locks are some devices that use electromagnets.
Brian Kross, Chief Detector Engineer (Other answers by Brian Kross)