A circuit diagram or wiring diagram uses symbols to represent parts of a circuit.
Electrical and electronic circuits can be complicated. Making a drawing of the connections to all the component parts in the circuits load makes it easier to understand how circuit components are connected.
During project days or workshops contact time with students is limited. It is therefore important for us to quickly ascertain student level of knowledge and then build on it or reinforce it. Analogies provide a good method of finding out students pre-existing level of understanding on this topic.
The standard return for electrical and electronic circuits is the earth ground. When an electrical or electronic device fails, it may open the return circuit to the earth ground.