Who invented Electricity?

Michael Faraday, Joseph Henry, 1853

Many see Michael Faraday, the bookbinder’s apprentice (and protégé of Humphry Davy) who rose to head London’s Royal Institution, as the greatest researcher of the 19^th century, or perhaps ever. His reputation rests mostly on his prodigious studies of electricity and magnetism over a period of 20 years.

History of Electricity:

He knew of the link the Dane Hans Orsted had found between electricity and magnetism. An electric current in wire is surrounded by magnetic field. In 1831 he asked ‘if electricity can produce magnetism, can magnetism produce electricity?. Anyone can do what he did. He wrapped a wire a number of times around one side of an iron ring, and connected the ends to a battery and switch. He wrapped a second coil around the other side of the ring and connected it to an instrument to report any current that flowed. He hoped to show that a current flowing in one coil would make the current flow in the other, the connection coming via the magnetic field.

Almost nothing happened. When Faraday turned on the current in the first coil, the needle in the galvanometer flicked quickly one way before settling back to zero. When he turned the current off again, the needle flicked the other way and returned to zero. So the magnetic field had to be changing, growing stronger or weaker, before it would make a current flow.

Faraday had found ‘electromagnetic induction’. A changing magnetic field ‘induces’ a current in a nearby wire. The practical consequences were obvious. A machine with magnets and coils of wire constantly moving relative to each other would produce a sustained electric current, as an alternative to using a battery. Faraday’s first ‘dynamo’ spun a copper plate between the poles on a powerful magnet. A current flowed in the disc but energy wastage was high. Still the crucial principle had been demonstrated.

A year later French inventor Hippolyte Pixii replaced the disc with some coils of wire, holding them still and spinning the magnet. This began decades of research to find the best arrangement of coils and magnets, including electromagnets, to convert movement into electricity. Some designs produced a current in only one direction (direct current or DC); other designs produced alternating current (AC), which flowed back and forth.

Similar findings were being made across the Atlantic. Natural philosopher Joseph Henry was a major figure in the growth of American science in the 19^th century, with achievements as both a researcher and a statesman of science. In 1846 he left a post at what was later called Princeton University to become the first Secretary of the newly founded Smithsonian Institution in Washington, today one of the world’s great museums and laboratories in science and technology. He also helped found the National Academy of Science, the North American equivalent of the Royal Society.

These roles took him away from his own research but his reputation was already secure, particularly in electricity and magnetism. In the late 1820s he built on the discovery of electromagnetism and made powerful electromagnets by wrapping thousands of loops of current carrying wire around iron bars. Some of these powered the first electric telegraph in America which among other benefits allowed the rapid reporting of weather information and forecasts; Henry was instrumental in setting up a national system for the purpose.

Working independently, Henry built electric motors and discovered electromagnetic induction in the same year as Faraday. He took the matter further, discovering ‘self induction’ before Faraday did. Changing current in a coil of wire makes a changing magnetic field; that field in turn generates another current in the same coil opposing the first. So changing currents (including alternating ones) are impeded or ‘choked’ as they try to pass through a coil of wire. The more rapidly the current changes the more noticeable the effect. ‘Chokes’ or ‘inductors’ remain vital components of electronic circuits today. Henry’s contribution is commemorated in the unit of inductance: the henry.

Faraday and Henry both grasped the use of induction in a ‘transformer’. If two coils are wound on the same piece of iron, the first with a few turns of wire, the second with many, the induced current in the second coil has a much higher ‘voltage’ than the first. So voltages can be ‘stepped up’ but only with alternating currents (AC); steady ‘direct’ current in the first; otherwise energy would be created. Raising the voltage lowers the current, and vice versa, an important consideration in the later ‘Battle of the Current’ as the use of electricity began to spread.