Now it’s time to put these ideas to work.  As was presented earlier the three elements required of electrical circuits are a source of electrical potential difference, an electrical load, and a complete conducting path connecting the two.

A schematic diagram (or circuit diagram) is used to show the organization and connections of the circuit.  Here is the simplest of electrical circuits.

Note that the potential difference is represented by two unequal lines with the longer of the two being the positive charge.  The load is not specified, but drawn generically as a sawtooth line.
 
 

A closed circuit provides a complete path for the charge carriers and results in a current.  An open circuit is an incomplete path and will not allow a current.

Only closed circuits allow the use of electrical energy.  Charges never go into dead ends.

Circuits rarely contain a single loads.  Usually they are made of combinations of loads.  No matter how complex a circuit is Ohm’s law and Watt’s law apply to the circuit as a whole as well as any part of the circuit.

Real circuits get very complex, but when they are broken down there are only two ways loads can be connected together; series and parallel connections.

A series connection provides only one path for the charges to follow.  If the charges go through one load they have to go through them all.

   A parallel connection provides multiple paths for the electrons to follow.  Charges may go through one load without going through any others.