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:
“Whoever influences the child’s life ought to try to give him a positive view of himself and of his world. The child’s future happiness and his ability to cope with life and relate to others will depend on it.”
—Bruno Bettelheim (20th century)
“Parents need to recognize that the negative behavior accompanying certain stages is just a small part of the total child. It should not become the main focus or be pushed into the limelight.”
—Saf Lerman (20th century)