2020 October 01 Thursday
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CLASS-10 -PHYSICS – Electromagnetic induction

Magnet An object that is surrounded by a magnetic field and that has the property, either natural or induced, of attracting iron or steel. According to one Greek legend, the name magnet was taken from the shepherd Magnes  who discovered the magnetic stone by accident when his staff was mysteriously attracted to the force of the stone. Another, and perhaps more believable, theory says that the word magnet came from a city in Asia Minor, called Magnesia, where many of these mysterious magnetic stones were found.

Different types of magnet
There are many different types of magnets.  Permanent magnets, Temporary magnets and Electromagnets. A permanent magnet is a magnet that does not lose its magnet field. Temporary magnets are those which act like a permanent magnet when they are within a strong magnetic field, but lose their magnetism when the magnetic field disappears. Electro magnet are adjustable by changing the magnitude of the current flowing through the wire and by changing the direction of the current flow.

Electromagnetic induction
Electromagnetic induction is the production of an electromotive force (emf) in a conductor as a result of a changing magnetic field about the conductor. It was discovered in 1831 by Michael Faraday and independently by Joseph Henry. 1821 Faraday discovered electromagnetic rotation. After few years  Faraday noticed that when he moved a permanent magnet in and out of a coil or a single loop of wire it induce an ElectroMotive Force or emf, in other words a Voltage, and therefore a current was produced.

A long straight coil of wire can be used to generate a nearly uniform magnetic field similar to that of a bar magnet. Such coils, called solenoids.

The galvanometer is used to measure very low currents, such as those in bridge circuits. The galvanometer consists of a coil of wire often rectangular, carrying the current to be measured.


Difference between  AC and DC generator



Both AC and DC generators produce currents via electromagnetic induction. In AC generators, the coil through which the current flows is fixed. It have two commutators. It is used to power for smaller motors and electrical appliances at home. In AC generator uses slip ring and brush. Here does not use of commutator


DC generators, the coil through which the current flows rotates in a fixed field. The two ends of the coil attach to a commutator: different halves of a single, rotating split ring. Metal brushes connect these split rings to an external circuit. It have only one commutator. It is used for functional in supplying power to heavy motors.

it is a passive two-terminal electrical component which resists changes in electric current passing through it. An inductor is a passive electronic component that stores energy in the form of a magnetic field. In its simplest form, an inductor consists of a wire loop or coil.



Michael Faraday

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Michael Faraday was one of the most prolific scientists of the 19th century. Michael Faraday, who came from a very poor family, became one of the greatest scientists in history. A British physicist and chemist, Faraday is best known for his discoveries of electromagnetic induction.  his other most notable discoveries are Electromagnetic Rotation, Gas Liquefaction and Refrigeration, Discovery of Benzene, Laws of Electrolysis, Faraday Cage. The unit of electrical capacitance is named the farad in his honour, with the symbol F.
Faraday was born on September 22, 1791 in  in Newington Butts today a part of the London, England, UK. He was the third child of James and Margaret Faraday. His father was a blacksmith who had poor health.

Michael Faraday attended a local school until he was 13, where he received a basic education. To earn money for the family he started working as a delivery boy for a bookshop. After a year, he was promoted to become an apprentice bookbinder. that time Faraday read many books .Faraday’s keen interest in science, especially in electricity, was developed herein. In 1812, at the end of his apprenticeship Faraday was presented tickets to attend four lectures to be delivered by the eminent professor of chemistry, Humphry Davy and John Tatum, founder of the City Philosophical Society, at the Royal Institution

 Faraday, in an attempt to thank Davy, sent him a three-hundred page book which contained notes taken during the lecture. Later, Faraday bagged a temporary job as a secretary to Davy, when the latter damaged his eyesight in an accident with nitrogen trichloride. In March 1813, Davy appointed Faraday as Chemical Assistant at the Royal Institution.
After just seven months at the Royal Institution, Davy took Faraday as his secretary on a tour of Europe that lasted 18 months. During this time Faraday met great scientists such as André-Marie Ampère in Paris and Alessandro Volta in Milan. In some ways, the tour acted like a university education, and Faraday learned a lot from it.  Faraday unhappy for much of the tour. Davy’s wife refused to treat Faraday as an equal, because he had come from a lower class family. In the year 1821, Faraday was appointed as the acting superintendent of the house of the Royal Institution.

On 12 June 1821 Faraday married Sarah Barnard. He and his bride lived in rooms in the Royal Institution for most of the next 46 years. Faraday’s contribution to chemistry was while he was working as an assistant to Davy. He was involved in the study of chlorine. Faraday also conducted experiments on the diffusion of gases. Additionally, he succeeded in liquefying several gases, investigating the alloys of steel, and producing several new kinds of glass intended for optical purposes. One of Faraday’s most notable works was invention of the earliest form of Bunsen burner. In 1825, aged 33, he became Director of the Royal Institution’s Laboratory. in 1831 Michael Faraday discovered electromagnetic induction, the principle behind the electricity generator.in 1833, aged 41, he became Professor of Chemistry at the Royal Institution of Great Britain. He died on 25 August 1867 at Hampton Court.


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