His greatest achievement was finding a practical application for alternating current. Tesla developed a multiphase electric motor in which he used the properties of this current to create the effect of a rotating magnetic field, putting the device into rotary motion. The alternating current made it possible to transmit energy over long distances by using transformers to raise the voltage. Tesla's opponents (supporters of Edison and thus of direct current) believed that alternating current carried a greater risk to life. Nevertheless, the two systems were still used parallel during the interwar period.
