So…. What is a Circuit?

By Perry Henderson

Perhaps the core concept of electronics is the concept of the circuit. I was told when I first started in electronics to “think of the circuit like a circle.” This basic mental image has served me well in thinking about circuits of all kinds. A circuit simply is a closed path that facilitates the flow of current. This current will then enable electrons to flow that will power various electronic components and ultimately, systems. The basic components of any circuit will consist of a type of power supply and or battery. That circuit will have wires or pathways which will serve as a conductor and various components such as capacitors and resistors. These components will complete some type of work. The electrons will flow from the negative terminal, through the circuit and its components, and then back to the positive terminal. This entire process forms a circle of electrons moving in a complete and flowing ring of electricity.

We have covered in a previous post the concepts of Ohm’s Law. Ohm’s Law as a refresher is V = IR. V is voltage, I is current, and R is resistance. We have also covered earlier the concepts of AC and DC. AC is alternating current; this means that the current basically changes direction. DC or direct current is current that is stable and moves in one direction (these are overly simple descriptions, but I’m trying to keep it simple). There are many different applications for each type of current. AC is utilized for power grids and homes, and DC is utilized in common electronics that you would buy at a store and in batteries.

Circuits can range from simple circuits such as door ringers and light bulbs to much more complex circuits such as those found in computers. The basic circuit will have voltage supplied from a battery, a switch of some kind that will open and close the circuit, and a load which would be the ringer or the bulb. If one looks at more complex technology, all technologies are still utilizing circuits, they just contain many more components and have a more complex system purpose. Experienced electricians or hobbyists often mention open or closed circuits. An open circuit simply has a gap that prevents the flow of electrons. A closed circuit is a circuit where there is no break to prevent the flow of current. When electricity encounters a low-resistance pathway, there can be dangerous heating, and the components of the circuit can be damaged significantly.

Remember that a circuit is largely just a circle of components and conductors that allow electricity to do its work. If one masters these basic principles one can become a solid electrical engineering hobbyist or maybe professional. Circuits serve the basis for most of the world’s modern technology, systems and innovation. Think circularly, friends.

The Amateur Electrical Engineer