The homopolar motor was created by Michael Faraday and was first demonstrated in 1821. After electromagnetism was discovered by Hans Christian Orsted, Humphry Davy and British scientist William Hyde Wollaston attempted to build an electric motor but they failed in doing so. Faraday went on his way to build two devices that create electromagnetic rotation after speaking with the two men. After he built the devices, he called one of them a "homopolar motor." The homopolar motor created a constant circular motion that was brought on by the magnetic force that was around a wire that went into a pool of mercury with a magnet inside of that pool. Faraday would then use a chemical battery to feed an electric current into the wire in order to make it rotate around the magnet. It is through these inventions that the base for electromagnetic technology has been set.
When a homopolar motor is reversed it then turns into a homopolar generator which then produces a direct current between the terminals of the conductor on the generator. During the 20th century these generators were researched as a way to create a low voltage but high current power supply. The results of this research can be seen in the United States Navy's experimentation with railguns. A railgun is based on the design of the homopolar motor. Although these railguns are perfect for combat situations they have several problems. The capacitors required to provide the power for these railguns are several cubic meters in size. The charge that comes from the electric current causes extreme heat to the rails and damages the surface of the rails. Due to the force that is pushed through the rails, this causes them to fall apart thus leaving the railguns useless after a few uses sometimes of being used once.
Although the United States military has to face these challenges, it is still interested in railguns due to the fact that the technology provides an alternative to using large artillery. The ammunition used by a railgun would be very easy to handle, transport wouldn't be much of a challenge, and the ammunition would be very light. The missiles fired from railguns would be a lot more accurate due to their extremely high velocities. Homopolar motors not only apply to military technology but they can apply to everyday life as well. The homopolar motor can also be applied to electromagnetic trains. There is a coil called a guideway which then repels that magnets that are located on the undercarriage of the maglev train. This then causes the train to be levitated and once the train levitates an electric current is supplied into the coils inside that are contained in the guideway. This then creates a series of magnetic fields that push and pull on the train. Alternating the electric current that is supplied through the coils causes the polarity of the magnetized coils to change. The magnetic field at the front of the train then pulls the train forward because of these changes, while the magnetic field behind the train pushes the train thus adding more force and moving it farther. Since the train floats on air, this eliminates friction causing the train to be able to move at speeds that are faster than traditional train engines with wheels on them. This technology helps shorten the amount of time it takes to move from one location to another and is very useful in overcrowded countries such as China or Japan. This then makes journeys that would have taken over an hour to make by car shorten to just under 10 minutes. Other countries have attempted to build maglev trains in their own cities but it has been too expensive for the cities to maintain. Through these ways homopolar motors have been able to apply to real life situations.