perm filename B[B,PMP] blob sn#008022
filedate 1971-01-08 generic text, type T, neo UTF8
00100 It will be necessary to know a little about elementary electronics,
00200 and, to that end, we will briefly look at some Physics. All matter is
00300 composed of atoms. For our purposes, it will be adequate to consider atoms
00400 to be very small round objects, composed of a nucleus, surrounded by electrons.
00500 The number and arrangement of the electrons around the nucleus is determined
00600 by (determins?) the particular type of matter that the atom is an atom of.
00700 Some substances, called elements, are composed of only one type of atom.
00800 Other substances, called compounds, are composed of combinations of different
00900 types of atoms -- they are combinations of elements.
01000 The electrons of an atom are more or less free to move from one
01100 atom to the next. This movement of electrons is electricity.
01200 Some atoms hold on to their electrons more firmly that others, and,
01300 therefor, some matterials allow electric current to flow more easily than
01400 others. Substances which allow this flow to happen easily are called
01500 conductors; substances which do not allow this are called insulators.
01600 In general, metals are good conductors, and things like rubber, plastics,
01700 cloth, etc. are insulators.
01800 Two important electrical quantities are voltage and current.
01900 If there are two pieces of metal which are not connected together, and
02000 if one of them has significantly more electrons than the other, then
02100 there is a voltage between the two pieces of metal. Voltage is always
02200 measured between two points and indicates that one of the points has
02300 relatively more electrons than the other -- voltage indicates that
02400 electrons would like to flow from one point to another. If the two
02500 pieces of metal which have a non-zero voltage between them are connected
02600 together by a wire, then electrons will flow from the one with more
02700 electrons, to the one with fewer electrons, until the voltage becomes
02800 zero. This movement of electrons is current. Current is always measured
02900 at one point, and it indicates the number of electrons flowing past
03000 that point.