If you like blending smoothies, feeling the breeze from your ceiling fan, and browsing the web, you love electromagnets. You may not have known it before, but electromagnets are responsible for so many of today’s most loved conveniences and teaching tools that a world without them has become somewhat unimaginable.
But what is an electromagnet? Let’s start out by differentiating them from regular or “permanent” magnets, which are magnets whose magnetic field is not a result of electrical current. These magnets have a north and south pole that each attract their opposite poles and repel their same poles.
An electromagnet also has poles and a magnetic field, but only in the event than an electric current is passed over the metal. Without electric current, the magnet is simply a piece of ferromagnetic metal, meaning it has the potential to be a magnet, but is not a magnet without the help of humans and electricity.
If a job necessitates a magnet, why use an electromagnet (and make necessary the use of electrical energy) when a normal magnet would work just as well? Electromagnets are great for jobs that don’t need to be done… forever. There are a lot of situations in which it is really convenient to be able to turn a metal’s magnetism on and off.
Take for example the use of a giant electromagnet in a junkyard. If you used a normal magnet for that task, you’d run into huge problems just trying to transport it; it would be impossible to remove from the truck it was placed in, and actually would likely be impossible to place into the truck in the first place without accumulating other metal things like bicycles and parking meters. It sounds comical, but in today’s society it would truly be very dangerous to attempt to transport a magnet that large.
So how are they made? To answer that question, let’s rewind to 1873 when physicist James Maxwell studied the interaction between positive and negative electrical charges. He eventually determined that magnets have poles, i.e. individual points at which charge is focused, and that these charges repel or attract each other based on orientation. He also observed that a magnetic field was generated around a wire when electric current passed through it.
Using this principal, anyone can make a very simple electromagnet. Take a an insulated copper wire and wrap it around a metal rod. Connect one end of the wire to the positive side of the battery and one end of the wire to the negative side of the battery. Electrons will being to move from the positive side to the negative side via the copper wire, i.e. electricity will begin to flow. This in turn causes a magnetic field to develop around the copper wire, and the strength of that field is a direct product of how tightly wound the wire is around the iron rod.
The iron rod, up until this point, was composed is such a way that it had plenty of unpaired electrons spinning all in the same direction (this is how magnetic fields are generated). However, the rod was riddled with microscopic magnetic domains that pointed in every direction, so magnetic fields tended to cancel each other out remain weak. However, when the electric current runs over the rod and turns it into a solenoid, what’s happening is that the magnetic field of the wire penetrates the rod’s willy-nilly magnetic domains and causes them to align with the larger magnetic field of the wire. The more electric current, the more magnetized the iron rod (up to a certain point).