The batteries flow in equal and definite amounts each interval (second of time) along a given section of the wire (conductor). Figure 4 shows this expressed in graph form. Notice that “line” is straight and parallel to the zero line AB.
If we consider the current to be 5 amperes (Fig. 4), this means the current is 5 amperes steadily and continually.
Most house wiring systems supply alternating (A.C.) current. Remember that the electrons flow first in one direction in the conductor, then in the other direction. Figure 5 shows this reversal of electron flow in graph form and shows the value of the current at any particular instant.
Do not confuse this method of expressing alternating current with wave motion. The wave like curve is used merely to picture the different values of alternating current--everything above the zero line represents electron flow in one direction--below the zero line represents electron flow in the opposite direction. The amount of current flow at any particular instant is measured from the zero line.
Fig. 5
The crest of the wave curve represents maximum current flowing in one direction, the trough represents maximum current flowing in the opposite direction. The time it takes for the current to go from one maximum to the next maximum above the line (in the same direction) is referred to as the period (period of time) and in ordinary house current, this is one-sixtieth of a second. This is also referred to as a cycle of current because the current has started from zero, increased to maximum, decreased to zero, reversed its direction, reached maximum in the opposite direction and again returned to zero.
