The diagrams are a big help when workers try to find out why a circuit does not work correctly.
One way to make this topic more accessible is to use analogies (Lakoff and Johnson 2008). Analogies are examples which possess similar features, or work in a comparable manner, to the ideas that you wish to teach (Harrison and Coll 2007). They offer an excellent method of visualising difficult and unfamiliar concepts, or ideas that can not be directly seen.
Resistors and other circuit elements can be connected in series or in parallel. Resistance in series circuits is the sum of the resistance.
The point where those electrons enter an electrical circuit is called the "source" of electrons. The point where the electrons leave an electrical circuit is called the "return" or "earth ground". The exit point is called the "return" because electrons always end up at the source when they complete the path of an electrical circuit.