For the current to flow it must have a complete path of conductors. This complete path is called circuit. For example copper wires, which are conductors, are used to connect lamps in a circuit to complete the path for the flow of electrons. The battery is also attached to the circuit to push the electrons around. To draw the complete path of flow of electrons on a paper, we use circuit diagrams with symbol for every part of the circuit. Following are some common circuit symbols.
Direct and alternating currents (d.c. and a.c. currents)
The electrons constantly flowing around the circuit, from the negative terminal of the battery to the positive terminal, produce direct current (d.c). All batteries produce direct current. In the mains electricity at homes, the electrons in the circuit move backwards and forwards 50 to 60 times in one second. This kind of current is called alternating current (a.c.). The main advantage of using alternating current over direct current is it can be transmitted from power stations to our homes at very high voltage which reduces the amount energy that is lost during the transmission.