different electrically charge
ELECTRICAL UNITS
We have discussed the big picture, so now some of the fine details must be explained. We will use standard units of measurement so that independent measurements can be related and have the same meaning.Three of these units are in common use: the volt, which is a measure of the electrical pressure; the amp, a measure of electrical current; and the ohm, a measure of electrical resistance. The following terms are the foundation of any electric study.
JOULE
The basic unit of energy is the “joule,” whose symbol is J. This is a very small unit of energy; several hundred thousand joules are required just to operate an incandescent lamp over an hour or so. Note that the energy required to do work and the amount of work performed is one and the same. If it takes 250,000 joules an hour to power an incandescent lamp, then the energy required was 250,000 joules an hour, and the work performed was 250,000 joules an hour. If all this energy were converted into light, the lamp would be 100 percent efficient. It is not, however, so the total energy required is the work required to light the lamp plus the work wasted (usually as heat).
COULOMB
The basic unit of electrical charge is the “coulomb,” whose symbol is C. A coulomb is defined as a number of electrons. The electron is an entity that has one negative charge, the smallest amount of charge measurable. Theoretically, this amount of charge is indivisible. In other words, there are no half electron charges (actually, there are theorized partial charges in modern atomic physics, but the electron is the smallest negative charge for our purposes). A coulomb is the amount of charge represented by 6,250,000,000,000,000,000 electrons. Though this may seem a large number, it is not, as electrons, along with their charge, are really quite small.
CHARGE
Charge (symbol Q) is measured in coulombs. Stated arithmetically, for example, if Q = 15C, this means the amount of charge is 15 coulombs (don’t even think of doing it in electrons).
