MICHAEL FARADAY
IT is strange that the man who did most for the progress of
the science of electricity in the nineteenth century was the son of a
London blacksmith. That man was Michael Faraday. He did not get much
schooling, and what he did get was not more than reading, writing, and
arithmetic.
[Illustration: Fig. 66.--Michael Faraday.]
His spare time was passed at home or in the streets. At the age of
thirteen he was engaged as an errand boy to a bookbinder. After a year
of running errands he was apprenticed to the trade of bookbinder, but
the trade did not suit him at all, and all the time he could spare
from it he spent in making chemical and electrical experiments. When he
could get somebody to pay his admission fee, he attended lectures on
these subjects.
When Faraday came of age he heard four lectures delivered at the Royal
Institution in London by Sir Humphry Davy, the great Cornishman, who
invented the safety lamp for miners. He was fired with the ambition to
become a man of science. He had a great dislike for trade, and thought
that all men of science were good and kind, and that it was the science
which made them so. He took careful notes of the lectures, and when
they were finished, he had the happy thought of sending his notes to
Sir Humphry Davy, and explaining to him that his dearest wish was
to follow in his footsteps. Davy was the best man he could possibly
have written to on such a subject. He received Faraday’s letter very
kindly, and promised to find some scientific work for him as soon as
he could. He kept his word, and engaged Faraday the very next year as
his assistant at the Royal Institution. At the age of thirty Faraday
married, and brought his wife to the Royal Institution, where they
lived together for six years. In that institution Faraday, in the year
1825, succeeded Davy as director.
Faraday’s first great achievement in electricity was to prove that
an electric current could be produced by means of a magnet, without
any electric battery. He made this discovery in the year 1831.
Eleven years previously, the first connection between magnetism and
electricity was discovered in Denmark. It was found that when a wire is
stretched under a magnetic needle in the direction in which the needle
points, and a current is sent through the wire, the needle turns round
and tries to set itself in a direction across the wire. In this way an
electric current produced some effect upon a magnet. Shortly after that
fact was discovered, a great Frenchman of the name of Ampère found that
one electric current attracts another that flows in the same direction,
while it repels a current which flows in the opposite direction.
It struck Faraday that it might be possible to produce an electric
current in a wire by simply starting a current in a neighbouring
battery. He tried the experiment by stretching two wires side by side,
and attaching the ends of one of the wires to an electric battery. In
order to discover whether a current was travelling through the second
wire, he brought a little magnetic compass up to it to see if the
compass would set itself at right angles to the wire and so indicate
a current. The needle indicated no current. Faraday then attached the
ends of the second wire to an instrument called a galvanometer. That
instrument consisted of a coil of wire in the centre of which the
magnetic needle was placed. The current would pass through the coil
of wire over the needle in one direction and under the needle in the
opposite direction, and in each case it would tend to set the needle at
right angles to the coil. The more turns the coil of wire had, the more
powerful would be the effect. In this way, therefore, Faraday hoped to
observe even a very small current.
But however long the current was kept passing through the first wire,
the galvanometer showed not the slightest current in the second wire.
This appeared very strange, because it was known that bodies may be
made electric, or magnetic, by bringing them into the neighbourhood
of electrified or magnetised bodies. It was natural, therefore, to
suppose that a coil of wire could be made to carry an electric current
by bringing it into the neighbourhood of another coil of wire which was
already carrying an electric current. But in such things it is useless
to endeavour to answer questions offhand. The only proper way is to try
an experiment. Faraday did try the experiment as already described, and
the result showed him that he was mistaken.
But Faraday was not discouraged easily. Thinking that perhaps the
effect could be strengthened by winding the wires round a piece of soft
iron, he took a ring of iron and wound two coils of wire round it,
taking care that no part of the wire was touching any other part, or
touching the iron. He then observed a curious effect, which was quite
different from what he had expected. He found that the galvanometer
gave a little start as soon as he turned on the current in the first
coil. Then it came to rest again, although the current was still
flowing. On turning off the current, the galvanometer gave a little
start in the opposite direction, and soon returned to rest again.
Faraday was in doubt whether this was really such an effect as he had
been looking for. He wrote to a friend, “I think I have got hold of a
good thing, but cannot say. It may be a weed instead of a fish that
after all my labour I have at last pulled up.”
Faraday was a first-class experimenter, and his method is a good
example of truly scientific work. When he found an effect which he
could not quite account for, he changed the experiment in a great many
different ways, in order to disentangle the causes and effects. The
next time he tried to obtain a current by means of a magnet instead
of another current. He took a natural magnet and wound a long coil of
wire round and round it. The natural magnet had a cap of iron, and on
pulling the cap off, a short momentary current appeared in the coil of
wire. This momentary current could be shown either by attaching the
ends of the coil of wire to a galvanometer or by bringing them close
together. When that was done a small spark passed between the two ends
of the wire.
This was another remarkable discovery, and Faraday proceeded to put it
into another different shape. He wound a coil of wire round a bar of
soft iron, and connected the ends with a galvanometer. Nothing happened
so long as the bar of iron was not magnetised. But on suddenly placing
the bar of soft iron between the two poles of a magnet, the bar became
magnetised, and the galvanometer gave a momentary start. He removed the
magnet, and the galvanometer gave a start in the opposite direction.
Faraday expressed this by saying that a momentary current is induced
in a coil of wire by starting or stopping a current in a neighbouring
coil, or by creating or destroying a magnet near the coil.
Such induced currents are also called “induction currents.” They are
familiar to many through the “induction coils” which are used to give
electric shocks. In these induction coils there is a cylinder of iron
surrounded by a coil of copper wire, and another coil of very fine wire
round that again. A current is started and stopped in rapid succession
in the first coil, and each starting and stopping induces a momentary
current in the outer coil. These momentary currents are made to travel
through the person who holds the handles. It is they that produce the
curious pricking sensation.
[Illustration: Fig. 67.--Induced Currents.]
Instead of sending a current through one coil inside another, we
may take a coil through which a current is already passing, and put
it inside another coil connected with a galvanometer. Each time
the current-bearing coil is put in or taken out, the needle of the
galvanometer moves, showing that a momentary current is passing through
it.
When we consider that great cities are now lighted by means of these
induced electric currents, it will be understood what a vast importance
Faraday’s discovery bore within itself. When we pass the electric light
works, a “central station” as it is called, we hear the throbbing of
the engines which turn the machines designed to produce the electric
current. These machines are called “dynamos.” A dynamo consists of
two things. One of them is a great magnet which produces a powerful
magnetic field. The other is a set of coils of wire which, driven by a
steam engine or gas-engine, move through the magnetic field.
[Illustration: Fig. 68.--A Simple Dynamo.]
Each coil, as it moves in and out of the magnetic field, becomes the
bearer of a momentary induction current, for to move a coil through
a magnetic field produces the same effect as to make or unmake an
electromagnet near the coil, or to start or stop a current in a
neighbouring coil.
Great inventors have been working ever since Faraday’s time to improve
and perfect the dynamo; some worked at collecting all the momentary
induced currents into one smooth current always flowing in the same
direction; others at providing ways and means for increasing the
strength of the magnetic field or the speed of the engines. And
thus to-day we have a vast industry occupying millions of men the
world over, all due to a man who worked quietly and steadily in his
laboratory, observing everything, neglecting nothing, and extracting
the nuggets of golden truth from the mean-looking dust and dross of
commonplace facts.
[Illustration: Fig. 69.--Dynamos in an Electric Light Central Station.]
Faraday made a great number of other discoveries. He investigated the
connection between chemistry and electricity, and founded a new science
called “electrochemistry.” He also studied the action of a magnet
on light, and found that a strong magnet is able to give a certain
twist to a beam of light while it passes through certain substances
(such as sulphide of carbon). Whenever he made such a discovery he
was transported with delight. He was always of a vivacious and merry
disposition. He said of himself: “I was a very lively, imaginative
person, and could believe in the Arabian Nights as easily as in the
Encyclopædia; but facts were important to me, and saved me. I could
trust a fact, and always cross-examined an assertion.”
Towards the end of his life he suffered greatly from loss of memory.
He helped himself by carrying about in his waistcoat pocket packets
of cards, on which he wrote everything he wanted to remember. One of
these has been preserved, and on it are found the following excellent
maxims:--
“Remember to do one thing at once. Also to finish a thing. Also to do a
little if I could not do much.”