VOLTAGE

Voltage is an electric potential difference between two points. Voltage is measured in volts. Voltage comes from various sources. Two examples of these sources are batteries and electrical outlets.  The electrical outlets in the wall have a very high and dangerous voltage.  Never connect anything to the electrical outlet.

The voltage source in a schematic is represented by the symbol below.  The short (bottom) end is the negative side where electrons leave from the voltage source and the long line (top) is the positive end of the voltage source.