Michael Faraday (1791–1867) was the son of a London blacksmith. He left school at 13 and was apprenticed to a bookbinder, where he read the science books he bound. In 1812 a customer gave him tickets to hear Humphry Davy lecture at the Royal Institution. Faraday wrote up his notes, bound them, and sent them to Davy. In 1813 Davy hired him as a laboratory assistant. He stayed at the Royal Institution for the rest of his working life and became the greatest experimenter of his age.
Key idea
The motor, 1821
In 1820 Hans Christian Ørsted in Copenhagen found that a wire carrying current pushes a compass needle sideways. Faraday wondered: if a current pushes a magnet, could a magnet push a current-carrying wire around and around? In September 1821 he hung a wire into a cup of mercury with a magnet standing in the middle, and connected a battery. The wire swept in circles around the magnet: the first device to turn electricity into continuous motion.
Induction, 1831: the key is change
If electricity can make magnetism, can magnetism make electricity? Faraday tried for years. On August 29, 1831, he wound two coils of wire on an iron ring, one joined to a battery and the other to a galvanometer, a meter for current. When he connected the battery, the needle jumped, then went back. When he disconnected it, the needle jumped the other way. While the current flowed steadily, nothing happened.
One of these helices was connected with a galvanometer, and the other with a battery of one hundred pairs of plates four inches square, with double coppers, and well charged. When the contact was made, there was a sudden and very slight effect at the galvanometer, and there was also a similar slight effect when the contact with the battery was broken. But whilst the voltaic current was continuing to pass through the one helix, no galvanometrical appearances of any effect like induction upon the other helix could be perceived.
Weeks later he tried a plain bar magnet and a coil.
One end of this magnet was introduced into the axis of the helix, and then, the galvanometer-needle being stationary, the magnet was suddenly thrust in; immediately the needle was deflected in the same direction as if the magnet had been formed by either of the two preceding processes. Being left in, the needle resumed its first position, and then the magnet being withdrawn the needle was deflected in the opposite direction.
Key idea
Worked example: Faster means more
- The same change happens in $\dfrac{0.5}{0.1} = 5$ times less time.
- So the voltage is 5 times larger: $5 \times 0.2 = 1$ V.
Answer: 1 volt.
That autumn he turned a copper disc between the poles of a big magnet and drew a steady current from it: the first generator, or dynamo. Joseph Henry in America found induction independently at about the same time; Faraday published first.
Teaching
Faraday began the Royal Institution's Christmas Lectures for young people in 1825, and they still run. His six lectures on The Chemical History of a Candle, given at Christmas 1860–1861, are among the most famous science talks ever printed.
There is not a law under which any part of this universe is governed which does not come into play, and is touched upon in these phenomena. There is no better, there is no more open door by which you can enter into the study of natural philosophy, than by considering the physical phenomena of a candle.
| When | What happened |
|---|---|
| 1791 | Born in Newington Butts, near London |
| 1805 | Apprenticed to the bookbinder George Riebau |
| 1812 | Hears Humphry Davy's lectures |
| 1813 | Becomes Davy's assistant at the Royal Institution |
| 1820 | Ørsted finds that a current moves a compass needle |
| 1821 | Faraday's electromagnetic rotation: the first motor |
| 1825 | Starts the Christmas Lectures |
| 1831 | Discovers electromagnetic induction; builds the first generator |
| 1832–1855 | Publishes Experimental Researches in Electricity |
| 1860–1861 | Lectures on The Chemical History of a Candle |
| 1867 | Dies at Hampton Court |
Worked example: From motor to generator
- $1831 - 1821 = 10$.
Answer: 10 years: a decade of trying.
What it led to
Every power station that spins a turbine, whether driven by steam, water or wind, uses Faraday's induction. So does every transformer. James Clerk Maxwell later put Faraday's ideas of fields into equations, which predicted radio waves. The unit of capacitance, the farad, is named after him.
Common mistake
Read the source on the Great Books Ladder
- Faraday: Experimental Researches in Electricity: the 1831 induction experiments in Faraday's own words
Read more: Michael Faraday.