2. Electric circuits
One speaks of a closed electric circuit if there is an electron flow between two poles over a conductor including resistors. The electrons flow from the negative pole (-) to the positive pole (+). Resistors in this sense can be e.g.: electric machines, electric devices, measuring instruments, electric components, light bulbs, etc... These resistors are also called power consumers.
In diagram 14, which shows a simple closed electric circuit, measuring elements for the measurement of the electric current and the voltage are drawn in using specially defined symbols according to DIN 40900 (German Industry Norm). Furthermore, voltage supply and resistance (power consumers) are drawn in with their corresponding symbols as well:
Diagram 14: Simple closed electric circuit