CH 18 a+b notes - 18.1 The Origin of Electricity Electrical...

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18.1 The Origin of Electricity Electrical nature of matter is inherent in atomic structure. o Simplified view of atom : heavy, positively charged nucleus orbited by one or more negatively charged electrons o Nucleus contains positively charged protons and electrically neutral neutrons o Charges on protons and electrons are of equal magnitude, but of opposite sign o In nature, atoms are normally found with equal numbers of protons and electrons, so they are electrically neutral. By adding or removing electrons from matter it will acquire a net electric charge with magnitude equal to e times the number of electrons added or removed, N. Atom is then called an ion. q = Ne It is possible to transfer electric charge from one object to another. The body that loses electrons has an excess of positive charge, while the body that gains electrons has an excess of negative charge. LAW OF CONSERVATION OF ELECTRIC CHARGE o During any process, the net electric charge of an isolated (closed) system remains constant (is conserved). Some molecules are intrinsically polarized (polar molecule). o Electrically neutral water molecule: equal amounts of positive & negative charge (10 protons & 10 electrons) center of positive charge and center of negative charge do not coincide electrons shared such that oxygen end has net negative charge and hydrogen atoms have net positive charge. Not only can electric charge exist on an object, but it can also move through and object. o Substances that readily conduct electric charge are called conductors. o Materials that conduct electric charge poorly are called insulators. o Metals are excellent conductors, with gold, copper, and aluminum being among the best. o Metals are excellent conductors because there are many “free” electrons (the outer electrons of a metal are very loosely bound and come loose very easily so they can wander around through the metal).
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CH 18 a+b notes - 18.1 The Origin of Electricity Electrical...

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