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College Physics

Xiaolong Jiang

Jay

Nanjing university of information science & technology

Plato (427-347 BC) in the 4th-century BC along with many others, thought that the amber effect and that of loadstone were closely interrelated. In China Wang Chong (AD 27-96) in Eastern Han Dynasty recounted the compass in his work.

The modest inscription on his tomb reads: “He wrote a book, concerning the magnet, celebrated among foreigners and among those engaged in nautical affairs.” William Gilbert - "the Galileo of magnetism" , graduated from Cambridge University. the fame of which he achieved lay in his book On the Magnet which concentrated primarily on magnetic phenomena.

Charles Augustin Coulomb (1736-1806) invented an instrument called the torsion balance - which later showed great utility for measuring very small electrical forces.

Coulomb stated that the electrical force between two electrified objects is proportional to the inverse square of the distance between them and to the product P of their electrical masses. This achievement marked the point where electricity became thoroughly open to mathematical analysis. 2 1 2

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Just over a month after the discovery, Jean-Baptise Biot (1774-1862) and Felix Savart (1791-1841) were the first to provide a precise analysis of the effect. Biot and Savart announced the Biot-Savart Law which can be used to calculate the magnetic field for a segment of current carrying wire. 3

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 Andre-Marie Ampere (1775-1836) was the first person to develop a technique for measuring electricity. he built an instrument which later refined being known as the galvanometer. Ampere’s theories became fundamental for 19th century developments in electricity and magnetism. Ampere’s law Ampere’s circulation theorem

Maxwell ’ s equations predicted that the phenomenon of light was electromagnetic in nature. Maxwell ’ s equations summarized a series of experimental laws in the field of electromagnetics.

In 1888 the German physicist Hertz (H. Hertz, 1857-

1894. firstly discovered the electromagnetic wave predicted by the Maxwell equations, thus the theoretical system of the classical electromagnetism was finally established.

Outline of part 2 Outline of part 2 Electrostatic Field (^) The field distributed round a static charge is called the electrostatic field. E  U Two Important Physical Quantities Force Work Two Fundamental Theorems Field with sources (^) Gauss’s Law conservative field Circulation Theorem

Main Contents Main Contents  Coulomb’s Law ， Superposition Principle of Coulomb Force  (^) Definition and computation of E   Electric Flux, Gauss’s Law  Circulation Theorem of electrostatic field, Electric Potential E   The relationship of and potential gradient  Motion of charged particles in electric field

§2.1 Point Charge, Coulomb’s Law §2.1 Point Charge, Coulomb’s Law

1. Properties of Electric Charges 1. Properties of Electric Charges A charged body without size and shape, i.e., a charged geometrical point. (1) Two Kinds of Electric Charge (1) Two Kinds of Electric Charge  Positive Charge, Negative Charge  Like charges repel each other, and unlike charges attract each other. Where “like” means two charges with the same sign.

 When the girl touches a Van de Graaff generator, she received an excess of positive charge, causing her hair to stand on end.