Positive and Negative
In DC circuits, the positive pole is usually marked red (or "+") and the negative pole is usually marked black (or "-"), but other color schemes are sometimes used in automotive and telecommunications systems. On a car battery, the positive pole usually has a larger diameter than the negative pole.
In AC systems which are at no point connected to earth (unlike domestic mains wiring where the neutral is commonly earthed at substations and generators) polarity is not important as the two wires alternate polarity many times per second.
Read more about this topic: Electrical Polarity
Famous quotes containing the words positive and/or negative:
“Property is the fruit of labor—property is desirable—is a positive good in the world.”
—Abraham Lincoln (1809–1865)
“The negative cautions of science are never popular. If the experimentalist would not commit himself, the social philosopher, the preacher, and the pedagogue tried the harder to give a short- cut answer.”
—Margaret Mead (1901–1978)