Faraday: Experimental Researches in Electricity

Michael Faraday was born in London in 1791. His family was poor, and he left school at 13 to work for a bookbinder. While he sewed books together, he read them, especially the ones about science. He went to hear a famous chemist, Humphry Davy, give lectures, wrote out neat notes, and sent them to Davy. Davy gave him a job as his helper.

Scientists already knew that electricity flowing in a wire makes it act like a magnet. Faraday asked the opposite question: can a magnet make electricity? He tried for years. In 1831 he found the answer. A magnet sitting still inside a coil of wire does nothing. But when he pushed the magnet in or pulled it out, a needle on his meter jumped. A moving magnet makes electricity flow!

That discovery runs our world. Almost all the electricity in your house is made in power stations by spinning magnets and coils of wire, just as Faraday found.

Faraday also loved teaching children. Every Christmas he gave lectures for young people at the Royal Institution in London. The most famous ones are about a single candle: what it is made of, why the flame has its shape, and where the wax goes when it burns.

Who, when and the problem

Michael Faraday (1791–1867) was the son of a London blacksmith. He was apprenticed to a bookbinder at 14 and taught himself science from the books he bound. In 1813 Humphry Davy hired him as an assistant at the Royal Institution, where Faraday worked for the rest of his life, becoming its director of the laboratory and its most famous lecturer. He had almost no mathematical training. His Experimental Researches in Electricity are 30 series of papers sent to the Royal Society from 1831 to 1855, each with numbered paragraphs, collected into three volumes (1839, 1844 and 1855).

The problem: in 1820 Hans Christian Ørsted found that an electric current turns a compass needle, so electricity can make magnetism. Many people suspected the reverse must also be true, that magnetism could make electricity, but experiment after experiment failed. A strong magnet next to a wire did nothing.

The main ideas

• Electromagnetic induction (1831). A changing magnetic effect makes a current. Switching a current on or off in one coil makes a brief current in a second coil wound on the same iron ring. Moving a magnet into or out of a coil does the same.
• The first generator. A copper disk spinning between the poles of a magnet gives a steady current (October 1831).
• One electricity. Current from batteries, from friction, from magnets, from electric fish and from heat are all the same thing (Third Series, 1833).
• The laws of electrolysis (1833–1834). The amount of a substance freed by a current is in proportion to the amount of electricity passed. With the scholar William Whewell he made up the words electrode, anode, cathode, ion and electrolyte.
• Lines of force and fields. Faraday pictured the space around magnets and currents as filled with curved "lines of force," which iron filings make visible. The forces live in the space, not only in the objects. This is the beginning of the idea of a field.
• Light and magnetism (1845). A magnet can turn the plane of polarized light passing through heavy glass (the Faraday effect), a first sign that light is linked to electricity and magnetism.

This is the key: nothing happens while the current is steady. Only the change, switching on or switching off, induces a current, and the two kicks go in opposite directions.

The candle

Faraday founded the Royal Institution's Christmas Lectures for young people in 1825 and gave nineteen series of them. The Chemical History of a Candle (lectures of 1860–1861, printed in 1861) follows a single candle into the chemistry of burning, the makeup of air and water, and our own breathing. Two of his popular lectures, on gravitation and on magnetism and electricity, from The Forces of Matter, are Harvard Classics readings.

Setting the record straight

• Joseph Henry, too. The American Joseph Henry found induction independently at about the same time and also discovered self-induction, but Faraday published first, in November 1831. The unit of inductance, the henry, honors him.
• Faraday did not invent the electric power industry by himself. His disk and his coils were laboratory devices that made tiny currents. Practical generators (from Hippolyte Pixii's in 1832 onward), transformers and power stations took the work of many engineers over the next 50 years.
• No math, but not no theory. Faraday's papers contain almost no equations, but they are full of careful reasoning about lines of force. James Clerk Maxwell wrote that he found Faraday's way of thinking to be mathematical in a deep sense, and turned it into equations.

What later science kept, and what it changed

• Kept: induction, the laws of electrolysis, the motor and generator principles, the Faraday effect and the words he coined. Faraday's law is one of Maxwell's four equations.
• Built on: Maxwell turned lines of force into the mathematics of fields (1855–1865) and found that light is an electromagnetic wave, as Faraday had guessed. Heinrich Hertz made such waves in 1887: radio.
• Changed: Faraday hoped gravity too would be linked to electricity and magnetism and searched for it without success. Gravity is still described separately, by Einstein's general relativity.

Fields, not forces at a distance. Newton had said he framed no hypotheses about how gravity reaches across space. Faraday's answer for electricity and magnetism was that the space itself carries the action: lines of force with real physical existence. In his 1846 lecture "Thoughts on Ray-Vibrations" he even suggested that light might be a vibration of those lines. Maxwell, Einstein and modern physics all think in terms of fields.

A notebook science. Faraday's laboratory diary runs to thousands of numbered entries. The Researches keep the same numbering, so he can refer back to an earlier paragraph like a proof refers to an earlier theorem. They are a rare chance to watch a great experimenter think, try, fail and try again.

Faith and science. Faraday was a lifelong member and elder of a small Christian church, the Sandemanians. He saw the laws of nature as a reflection of the order of creation, and kept his faith and his laboratory work as separate kinds of activity. Historians have discussed how his belief in the unity of nature's forces may have guided his search for links between them.

Teaching. Faraday's advice to lecturers was to show experiments, speak plainly and treat the audience as friends. His Christmas Lectures, still given every year at the Royal Institution, are a model for anyone who explains science to young people.

End of the science shelf. Faraday is the last scientist in volume 42 of the set. The next science on the ladder, Darwin (volume 49), turns from physics and chemistry to the history of life.