This Month in Physics History

September 4, 1821 and August 29, 1831: Faraday and Electromagnetism

Michael Faraday

British scientist Michael Faraday—the man who would contribute so much to our understanding of electricity and magnetism—had relatively humble beginnings. He was born September 22, 1791 the son of a local blacksmith in the area of London now known as the Elephant and Castle. He attended day school and learned the rudiments of reading, writing and arithmetic, but never pursued a more formal education. Instead, at the age of 14, he was apprenticed as a bookbinder for seven years, during which he developed an interest in science, particularly chemistry.

Faraday's natural inquisitiveness led him to read extensively on natural science and perform chemical experiments, even building his own electro-static machine. He also joined the City Philosophical Society in 1810, which was devoted to self-improvement in a group of young men who met every week to hear lectures on scientific topics and to discuss scientific matters. It was here that Faraday gave his first lectures, and also met Humphrey Davy, a professor of Chemistry at the Royal Institution. Davy appointed the young Faraday chemical assistant at the Royal Institution in 1813, thus steering his protégé in the direction of what would become an illustrious scientific career.

In 1820 the Danish natural philosopher Hans Christian Oersted had discovered the phenomenon of electromagnetism, which opened up a major field of scientific inquiry all over Europe. Faraday took part in this effort. On September 3, 1821, he undertook a set of experiments in his basement laboratory at the Royal Institution which culminated in his discovery of electromagnetic rotation-the principle behind the electric motor.

However, in the ensuing decade, Faraday's opportunity for doing original research was severely circumscribed, although he quickly became known as one of the outstanding scientific lecturers of his time. He liquefied chlorine in 1823 and discovered benzene two years later, but he didn't resume his work on electromagnetism until August 1831, when Faraday began ten days of intensive work which had a revolutionary impact. Ever since 1825, he had been wondering whether an electric current passing through a conductor could induce an electric current in a neighboring conductor.

Michael Faraday's laboratory. Inset image of Faraday's apparatus. (AIP Emilio Segrè Visual Archives; Inset: http://www.the-education-site.com/faraday.html)

On August 29th, he succeeded in accomplishing this with a six-inch diameter iron ring, around which were wound five coils of copper wire. One coil was connected to the voltaic pile and another to a galvanometer. The moment the current in the battery was active, a transitory current appeared in the galvanometer in the opposite direction. This now-famous induction cell was the first electrical transformer, and modern transformers-some of which have capacities of up to 550 MVA and contain more than 40 tons of copper-are still constructed on the same principle.

Faraday then proceeded to demonstrate that the lines of magnetic force could be cut, and a current induced, simply by rotating a copper disc by hand between the poles of a powerful electromagnet. This is now known as the principle of the dynamo, and soon found practical application in numerous small electric generators. It took several years for such generators to become efficient, but by 1841 power-driven multipolar machines were employed in Birmingham for the electroplating of copper articles, and by 1858 a generator for electric light had been installed in the North Foreland Lighthouse.

During the remainder of the 1830s, Faraday worked on developing his ideas on electricity, enunciating a new theory of electrochemical action from which were coined many words that are a staple of scientific research today: electrode, electrolyte, anode, cathode, and ion, to name a few. He also worked on a new theory of static electricity and electrical induction which led him to reject the traditional view that electricity was an imponderable fluid. Instead, he proposed it was a form of force that passed from particle to particle of matter.

In the 1840s, prompted by discussions with a young William Thomson (later Lord Kelvin), Faraday conducted a series of experiments that led to his discovery of the magneto-optical effect, today known as the Faraday effect. The mathematical underpinnings of this effect were developed by Thomson and, at his instigation, by James Clerk Maxwell, in whose hands it became one of the cornerstones of modern physics. Faraday continued working in science for two more decades, but chronic ill health eventually took its toll. He died at Hampton Court on August 25, 1867.