An electronic circuit is a complete course of conductors through which current can travel. Circuits provide a path for current to flow. To be a circuit, this path must start and end at the same point. In other words, a circuit must form a loop. An electronic circuit and an electrical circuit has the same definition, but electronic circuits tend to be low voltage circuits.
For example, a simple circuit may include two components: a battery and a lamp. The circuit allows current to flow from the battery to the lamp, through the lamp, then back to the battery. Thus, the circuit forms a complete loop.
Of course, circuits can be more complex. However, all circuits can be distilled down to three basic elements:
Voltage source: A voltage source causes current to flow like a battery, for instance.
Load: The load consumes power; it represents the actual work done by the circuit. Without the load, there’s not much point in having a circuit.
The load can be as simple as a single light bulb. In complex circuits, the load is a combination of components, such as resistors, capacitors, transistors, and so on.
Conductive path: The conductive path provides a route through which current flows. This route begins at the voltage source, travels through the load, and then returns to the voltage source. This path must form a loop from the negative side of the voltage source to the positive side of the voltage source.
The following paragraphs describe a few additional interesting points to keep in mind as you ponder the nature of basic circuits:
When a circuit is complete and forms a loop that allows current to flow, the circuit is called a closed circuit. If any part of the circuit is disconnected or disrupted so that a loop is not formed, current cannot flow. In that case, the circuit is called an open circuit.