Physics
Electron Specific Charge
Electron specific charge is the ratio of the charge of an electron to its mass. It is a fundamental constant of nature and has a value of approximately 1.76 x 10^11 coulombs per kilogram. This quantity is used in various calculations in physics, particularly in the study of electromagnetic phenomena.
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3 Key excerpts on "Electron Specific Charge"
- Andrei D. Polyanin, Alexei Chernoutsan(Authors)
- 2010(Publication Date)
- CRC Press(Publisher)
Chapter P3 Electrodynamics P3.1. Electric Charge. Coulomb’s Law P3.1.1. Electric Charge and Its Properties ◮ Electric charge is a scalar physical quantity that determines the electromagnetic inter-action of subatomic particles. In SI, the unit of charge is the coulomb (C); it is defined in terms of the unit of electric current, the ampere (A): 1 C = 1 A s. Properties of electric charge : 1. The carriers of electric charge are many subatomic particles such as protons and electrons (as well as antiprotons and positrons) and some metastable particles as π -mesons, K -mesons, muons, etc. Charged particles interact with each other with forces that decay with the distance as slowly as gravitational forces but are much stronger in magnitude. 2. Proton and electron and many other charged subatomic particles have the same electric charge in magnitude. This charge is called the elementary charge and denoted e . In SI, e = 1 . 602 × 10 – 19 C. As experiments have shown, the charge of subatomic particles is independent of their velocity. 3. The charge of subatomic particles can be either positive or negative. Particles with like charges repel one another and particles with unlike charges attract. By convention, the charge of a proton is positive (+ e ) and the charge of an electron is negative (– e ). If a macroscopic body includes different numbers of electrons, N e , and protons, N p , the body is charged and its charge is always multiple of the elementary charge: q = e ( N p – N e ). ◮ Law of conservation of electric charge. A system is called electrically closed if it does not exchange charges with external bodies, which means that charges do not cross its boundary. The total charge of an electrically closed system, or the algebraic sum of all its charges, remains constant. This statement is obvious if there are no elementary particle reactions. However, the law of conservation of charge is fundamental — it holds even if charged particles are created or destroyed.
eBook - PDFElectromagnetism for Engineers
An Introductory Course
- P. Hammond(Author)
- 2013(Publication Date)
- Pergamon(Publisher)
Since the current is measured in amperes, the unit of charge is the ampere-second and its special name is the coulomb. As we have also mentioned the forces due to the motion of charges are much smaller than those due to position. It is therefore convenient to choose the unit as involving the motion of a very large number of electrons. Thus in the SI system the electronic charge is chosen as 1-60 X 10 coulombs. The constant is experimental and is found to be 9 X 10^ (within 2 parts in 1,000). It is interesting to compare the electric and gravitational forces between two electrons. At a distance of 1 mm the gravitational force is an attraction of Electric Charges at Rest—I 11 because the subject of electrostatics had developed long before there was any knowledge of neutrons, protons and electrons. He will also have some misgivings that in our discussion we have included gravitational and electrostatic forces but have left out the short-range forces which bind the particles together in the atomic nucleus. Moreover he might rightly be suspicious about the exact nature of the experiments which supposedly led to the results described. It must at once be acknowledged that we have not followed the historical sequence. Many books on electricity have been written without reference to the fundamental particles, but since there are such particles there seems every reason to start our discussion by considering them. Nevertheless the laws of electromagnetism were originally applied to aggregates of electric particles and not to isolated particles or to nuclear structure. Additional considerations and laws have to be introduced when dealing with individual atoms. In this book we shall limit ourselves to the study of macroscopic phenomena and we shall treat electricity as a continuous fluid rather than as an assembly of discrete charges.
eBook - PDF- David Halliday, Robert Resnick, Jearl Walker(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
21.1.13 Identify that if a charged particle is located inside a shell of uniform charge, there is no net elec- trostatic force on the particle from the shell. 21.1.14 Identify that if excess charge is put on a spherical conductor, it spreads out uniformly over the external surface area. 21.1.15 Identify that if two identical spherical conduc- tors touch or are connected by conducting wire, any excess charge will be shared equally. 21.1.16 Identify that a nonconducting object can have any given distribution of charge, including charge at interior points. 21.1.17 Identify current as the rate at which charge moves through a point. 21.1.18 For current through a point, apply the relation- ship between the current, a time interval, and the amount of charge that moves through the point in that time interval. Key Ideas ● The strength of a particle’s electrical interaction with objects around it depends on its electric charge (usu- ally represented as q), which can be either positive or negative. Particles with the same sign of charge repel each other, and particles with opposite signs of charge attract each other. ● An object with equal amounts of the two kinds of charge is electrically neutral, whereas one with an imbalance is electrically charged and has an excess charge. ● Conductors are materials in which a significant number of electrons are free to move. The charged particles in nonconductors (insulators) are not free to move. ● Electric current i is the rate dq/dt at which charge passes a point: i = dq ___ dt . ● Coulomb’s law describes the electrostatic force (or electric force) between two charged particles. If the Coulomb’s Law C H A P T E R 2 1 642 CHAPTER 21 COULOMB’S LAW What Is Physics? You are surrounded by devices that depend on the physics of electromagnetism, which is the combination of electric and magnetic phenomena.
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