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definition

The quantity of electricity required to deposit or liberate 1 gram equivalent weight of a substance during electrolysis; approximately −96,487 coulombs.

At last, in 1845, Faraday attacked the old problem, but this time with complete success.

Faraday's term " electrode," literally " a way (650s) for electricity to travel along," might be well applied to designate the insulated conductor along which the electric messenger is despatched.

About the same time appeared his elaborate memoir, " On Faraday's Lines of Force," in which he gave the first indication of some of those extraordinary electrical investigations which culminated in the greatest work of his life.

The writer had the opportunity of perusing the MS. of " On Faraday's Lines of Force," in a form little different from the final one, a year before Maxwell took his degree.

Weber, which was found capable of explaining all the phenomena investigated by Ampere as well as the induction currents of Faraday.

He also investigated the diamagnetic and paramagnetic properties of substances; and was keenly interested in the phenomena of electrochemical decomposition, accumulating much evidence in favour of Faraday's law and proposing a modified statement of it which was intended to cover certain apparent exceptions.

Faraday's next step was to pass the same current through different electrolytes in series.

Faraday examined also the electrolysis of certain fused salts such as lead chloride and silver chloride.

Since Faraday's time his laws have been confirmed by modern research, and in favourable cases have been shown to hold good with an accuracy of at least one part in a thousand.

The opposite parts of an electrolyte, which work their way through the liquid under the action of the electric forces, were named by Faraday the ions - the travellers.

While it seems clear that the conduction in this case is carried on by ions similar to those of solutions, since Faraday's laws apply equally to both, it does not follow necessarily that semi-permanent dissociation is the only way to explain the phenomena.

This experiment suggested to Faraday the conception of ' r,?

Thomson (afterwards Lord Kelvin) in 1847, as the result of a mathematical investigation undertaken to explain Faraday's experimental observations.

But it was discovered by Faraday in 1845 that all substances, including even gases, are either attracted or repelled by a sufficiently powerful magnetic pole.

These are the " axial " and " equatorial " positions of Faraday.

Now iron, nickel and cobalt all lose their magnetic quality when heated above certain critical temperatures which vary greatly for the three metals, and it was suspected by Faraday 3 as early as 1845 that manganese might really be a ferromagnetic metal having a critical temperature much below the ordinary temperature of the air.

The critical temperature (if there is one) was not reached in Faraday's experiment; possibly even the temperature of -250 C., which by the use of liquid hydrogen has now become accessible, might still be too high.

Michael Faraday's researches were begun in 1831 and continued for more than twenty years.

In 1873 James Clerk Maxwell published his classical Treatise on Electricity and Magnetism, in which Faraday's ideas were translated into a mathematical form.

He failed in both respects, and when Michael Faraday, who overheard a portion of his conversation with Davy on the subject, was subsequently more successful, he was inclined to assert the merit of priority, to which Faraday did not admit his claim.

In 1824 the Royal Astronomical Society of London appointed a committee on the subject, the experimental' work being carried out by Faraday.

In 1868 he succeeded Faraday as Fullerian professor of chemistry at the Royal Institution, and in 1872 he was elected, in succession to Sir Benjamin Brodie, Waynflete professor of chemistry at Oxford, a chair he occupied for 40 years.

Faraday introduced the important and useful conception of lines and tubes of electric force.

Faraday expressed this fact by saying that no absolute electric charge could be given to matter.

Cavendish and subsequently Faraday discovered this fact, and the latter gave the name " specific inductive capacity," or " dielectric constant," to that quality of an insulator which determines the charge taken by a conductor embedded in it when charged to a given potential.

The student will find it to be a great advantage to read through Faraday's three volumes entitled Experimental Researches on Electricity, as soon as he has mastered some modern elementary book giving in compact form a general account of electrical phenomena.

Faraday applied it to the preparation of extremely thin films of the metal.

This subject he was led to study by the experience of a colliery engineman, who noticed that he received a sharp shock on exposing one hand to a jet of steam issuing from a boiler with which his other hand was in contact, and the inquiry was followed by the invention of the "hydro-electric" machine, a powerful generator of electricity, which was thought worthy of careful investigation by Faraday.

Faraday was first able to liquefy ammonia.

A train of ideas which strongly impressed itself on Clerk Maxwell's mind, in the early stages of his theoretical views, was put forward by Lord Kelvin in 1858; he showed that the special characteristics of the rotation of the plane of polarization, discovered by Faraday in light propagated along a magnetic field, viz.

Now the electric force (P,Q,R) is the force acting on the electrons of the medium moving with velocity v; consequently by Faraday's electrodynamic law (P,Q,R) = (P',Q' - vc, R'+vb) where (P',Q',R') is the force that would act on electrons at rest, and (a,b,c) is the magnetic induction.

Hence many of his investigations were first described by Faraday in his Friday evening discourses at the Royal Institution.

Churches of this order were founded in Paisley, Glasgow, Edinburgh, Leith, Arbroath, Montrose, Aberdeen, Dunkeld, Cupar, Galashiels, Liverpool and London, where Michael Faraday was long an elder.

Faraday himself became apprenticed to a bookbinder.

Faraday took notes of these lectures, and afterwards wrote them out in a fuller form.

Faraday's earliest chemical work was in the paths opened by Davy, to whom he acted as assistant.

A specimen of one of these heavy glasses afterwards became historically important as the substance in which Faraday detected the rotation of the plane of polarization of light when the glass was placed in the magnetic field, and also as the substance which was first repelled by the poles of the magnet.

But Faraday's chemical work, however important in itself, was soon completely overshadowed by his electrical discoveries.

Faraday was not there at the time, but coming in afterwards he heard the conversation on the expected rotation of the wire.

This first success of Faraday in electro-magnetic research became the occasion of the most painful, though unfounded, imputations against his honour.

Into these we shall not enter, referring the reader to the Life of Faraday, by Dr Bence Jones.

The thing cannot be done unless we adopt in some form Faraday's ingenious solution, by causing the current, in some part of its course, to divide into two channels, one on each side of the magnet, in such a way that during the revolution of the magnet the current is transferred from the channel in front of the magnet to the channel behind it, so that the middle of the magnet can pass across the current without stopping it, just as Cyrus caused his army to pass dryshod over the Gyndes by diverting the river into a channel cut for it in his rear.

During his first period of discovery, besides the induction of electric currents, Faraday established the identity of the electrification produced in different ways; the law of the definite electrolytic action of the current; and the fact, upon which he laid great stress, that every unit of positive electrification is related in a definite manner to a unit of negative electrification, so that it is impossible to produce what Faraday called "an absolute charge of electricity" of one kind not related to an equal charge of the opposite kind.

The first period of Faraday's electrical discoveries lasted ten years.

On the 3rd of November a new horseshoe magnet came home, and Faraday immediately began to experiment on the action in the polarized ray through gases, but with no effect.

The discovery of the magnetic rotation of the plane of polarized light, though it did not lead to such important practical applications as some of Faraday's earlier discoveries, has been of the highest value to science, as furnishing complete dynamical evidence that wherever magnetic force exists there is matter, small portions of which are rotating about axes parallel to the direction of that force.

The parents of Faraday belonged to the very small and isolated Christian sect which is commonly called after Robert Sandeman.

Faraday himself attended the meetings from childhood; at the age of thirty he made public profession of his faith, and during two different periods he discharged the office of elder.

And Faraday devised some simple apparatus which conclusively demonstrated that the movements were due to unconscious muscular action.

But Faraday's demonstration did little to stop the popular craze.