The function of magnetic energy was theorized by physicist James Clerk Maxwell in the 19th century as being comprised of both magnetic and electric forces. Maxwell's equations established the two forms of energy as operating under a single force, with each magnetic field generating a distinctive electrical current.
Maxwell's equations expanded upon known relations of electric and magnetic fields through determining that various forms of light are sources of electromagnetic energy that may be produced through transmitting magnetic currents through conducive materials. Electromagnetic energies vary depending upon their wavelengths, which visibly manifest themselves in a spectrum of colors that occur in natural phenomena, such as the Northern Lights.
Magnetic energy may be generated to attract other metal pieces or to store power in the form of batteries and dams. The hydroelectric power plant at Niagara Falls generates electricity through rotating magnetic field forces discovered by Nikola Tesla, who developed polyphase alternating current generators capable of changing the direction of voltage.
Electromagnetism is additionally harnessed in the form of direct current developed by Thomas Edison through devices called dynamos, which consist of magnets rotating within the influences of other magnetic fields. As with generators, dynamos include stationary and rotating magnets that respectively build magnetic fields and sever lines of magnetic flux. This process generates the electricity used in most contemporary and developing technologies.