If two small charged bodies of light weight are mounted so that they are free to move easily and are placed close to each other, one can be attracted to the other when the two charges have opposite polarity. In terms of electrons and protons, they tend to be attracted to each other by the force of attraction between opposite charges. Furthermore, the weight of an electron is only about 1/1840 weight of a proton. As a result, the force of attraction tends to make electrons move to protons.
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Negative and Positive Polarities
Historically, the negative polarity has been assigned to the static charge produced on rubber, amber, and resinous materials in general. Positive polarity refers to the static charge produced on glass and other vitreous materials. On this basis, the electrons in all atoms are basic particles of negative charge because their polarity is the same as the charge on rubber. Protons have positive charge because the polarity is the same as the charge on glass.
Read More......The Coulumb Unit of Charge
If you rub a head rubber pen or comb on a sheet of paper, the rubber will attract a corner of the paper if it is free to move easily. The paper and rubber then give evidence of a static electric charge. The work of rubbing resulted in separating electrons and protons to produce a charge of excess electrons on the surface of the rubber and a charge of excess protons on the paper.
Because paper and rubber are dielectric materials, they hold their extra electrons or protons. As a result, the paper and rubber are no longer neutral, but each has an electric charge. The resultant electric charges provide the force of attraction between the rubber and the paper. This mechanical force of attraction or repulsion between charges is the fundamental method by which electricity makes itself evidence.
Any charge is an example of static electricity because the electrons or protons are not in motion. There are many examples. When you walk across a wool rug, your body becomes charged with an excess of electrons. Similarly, silk, fur, and glass can be rubbed to produce a static charge. This effect is more evident in dry weather, because a moist dielectric does not hold its charge so well. Also, plastic materials can be charged easily, which is why thin, light weight plastics seem to stick to everything.
The charge of many billions of electrons or protons is necessary for common applications of electricity. Therefore, it is convenient to define a practical unit called the coulomb (C) as equal to the charge of 6.25 x 10^18 electrons or protons stored in a dielectric. The analysis of static charge and their forces is called electrostatics.
The symbol for electric charge is Q or q, standing for quantity. For instance, a charge of 6.25 x 10^18 electrons is stated as Q = 1 C. This unit is named after Charles A. Coulomb (1736-1806), a French physicist, who measured the force between charges.
Particles in the Nucleus
A stable nucleus, which is not radioactive, contains protons and neutrons. A neutron is electrically neutral without any net charge. Its mass is almost the same as a proton.
A proton has the positive charge of a hydrogen nucleus. The charge is the same amount as that of an orbital electron but of opposite polarity. There are no electrons in the nucleus. Table 3 lists the charge and mass for these three basic particles in all atoms.
Subshells
Although not shown in the illustrations, all the shells except K are divided into subshells. This subdivision accounts for different types of orbits in the same shell. For instance, electrons in one subshell may have elliptical orbits, while other electrons in the same main shell have circular orbits. The subshells indicate magnetic properties of the atom.
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