Great scientists
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Michael Faraday
English scientist Michael Faraday (1791–1867) rose from humble beginnings to become one of the greatest experimental physicists of all time. His work on the properties of electricity and magnetism revolutionized science and the technology that developed from it. He pioneered the electric motor and discovered how electricity could be generated. As a result of his work, electricity was transformed from a scientific curiosity into a powerful new technology.
Early life
Michael Faraday was born in Newington Butts, now part of south London, the son of a blacksmith. He was only 13 when his formal education came to an end, but he continued to educate himself. He was apprenticed to a bookbinder, and used the opportunities this gave him to read scientific books.
In 1812, he heard Sir Humphrey Davy (1778–1829), one of the foremost scientists of the day, give lectures at the Royal Institution, a centre for public debate and education about science. He became Davy's assistant in 1813. The following year Faraday travelled throughout Europe with Davy and his wife, meeting many famous scientists. Faraday married Sarah Barnard in 1821. The couple had no children.
Ørsted's experiment
Faraday’s lifelong study of electricity and magnetism began when he came across the work of the Danish physicist Hans Ørsted (1771–1851). Ørsted had discovered that if an electric current passes through a wire coil, it creates a magnetic field around it. The magnetic field pushed a compass needle away from it—like magnetic poles always repel one another. Temporarily, the wire coil became a magnet and the magnetic force acted around the wire.
Electric motor
Intrigued by Ørsted's findings, in 1821, Faraday built two pieces of apparatus (a diagram of his apparatus is pictured, left). In one (shown on the left), a bar magnet rotated in a flask of mercury, a liquid metal, round a wire carrying an electric current. In the other (shown on the right), the wire with the electric current moved round the magnet. With this experiment Faraday showed how electricity could be turned into a motive force, or movement. He had created the first electric motor.
Creating electricity
Faraday went on to show that, just as electricity could be used to create a magnet, so a magnet could be used to create electricity. In 1831, he devised three experiments to show this. The first one consisted of an iron ring with two lengths of wire coiled around opposite sides. Faraday discovered that when a current was started up through one coil, a current was created (induced) in the other—but only when the current was started up, not when there was a steady current.
In Faraday's second experiment, every time a cylindrical magnet was pushed into a wire coil or pulled out, it produced an electrical current in the coil. In the third, a copper disc was inserted between the arms of a horseshoe magnet. When the disc was spun, a continuous electric current flowed through it. Faraday had created the forerunner to the dynamo, a basic electric generator. The disc came to be known as the Faraday's disc.
Electromagnetic induction
Faraday now understood that electricity and magnetism were two aspects of the same force: the electromagnetic force. He could now propose his Law of Induction: an electric current is generated in a conductor (any material through which an electric current can pass) whenever the magnetic field in the region of the conductor is changing.
Using magnetic force to generate electricity is called electromagnetic induction. The principle is still used in power stations today.
Nature of electricity
Faraday’s work with electricity led him to understand what it is and how it behaves more than any scientist before him. He understood that static electricity—lightning, for example—and current electricity are the same thing, and that electricity can generate a force.
In the 1830s, Faraday carried out experiments in electrolysis. He placed two electrodes (metal rods) into a solution of tin chloride and connected a supply of electricity to them. The electric current travelled between the electrodes through the tin chloride solution. As it did so, it caused the solution to break down into its constituent parts: tin and chlorine. Faraday worked out the laws of electrolysis, to explain the processes he had observed in his experiments.
Faraday Effect
At the end of the 1830s, Faraday’s health broke down, and for several years he did little work at all. At work again in the 1840s, he was convinced that there was a unity of forces in nature—that all the forces, such as gravity, magnetism and electricity, could be converted into one another.
In 1845, he went some way to proving this when he discovered that magnetism could have an effect on polarized light (beams of light that are concentrated on a single plane instead of spreading out in all directions, as they usually do). By applying a magnetic force he could actually make the beam spin round. This is called the Faraday Effect. Faraday wrote: "I have at last succeeded in ... magnetizing a ray of light."
He had established that magnetic force and light were somehow related.
Consultant: Mike Goldsmith