These motors are ideal for clocks and telescopes, which require precise timing and smooth turning. Universal motors are built to operate on either DC or AC electricity. A universal motor uses a commutator, and its basic construction resembles the design of a DC series motor. On DC, it performs like a series motor. If AC is used, the magnetic poles of the armature and the field coils reverse with the frequency of the current.
Universal motors are popular in many appliances because of their flexibility.
The development of electric motors began in the 1800's with the discovery of electromagnets. In 1820, a Danish physicist named Hans Christian Oersted discovered that a wire conducting an electric current produces a surrounding magnetic field. During the 1820's, a number of other scientists found ways of creating stronger and more practical electromagnets. In 1825, William Sturgeon, an English electrician, wrapped a conductor around an iron bar to produce a stronger electromagnet. In the late 1820's, the American physicist Joseph Henry showed that an even more powerful electromagnet could be made by wrapping several layers of insulated wire around a piece of iron.