What do You Need to Make A Simple Electrical Circuit?

There are electrical and electronic circuits all around us, and most of them are not so simple. Just look at your phone, that’s probably one of the most complex electronic equipment around us. Or look at your home’s electrical circuitry, it’s not just complicated but also very dangerous. If we understood the most basic building blocks of an electrical circuit, we might be able to understand more complex ones and more importantly, keep ourselves safe from the dangers of electricity. So, what do you need to make a simple electrical circuit?

You need four things to make the simplest electrical or electronic circuit.

  1. A power supply
  2. A load
  3. A control device
  4. A current path

Let’s look at each in some detail

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Where does an electrical circuit gets the electrical energy?

All electrical and electronic devices need a power source – a source that provides them with voltage and current. Voltage and current together are called electrical power and power provides electrical energy to the equipment, which then does something for us.

For example, the battery in your phone is a power supply that electrical energy to your phone. A socket outlet supplies the electrical energy to your home appliances like a toaster. Solar panels provide the electrical energy that charges your batteries.

Rating and specifications of a power supply

To power any equipment, the first thing you need is a power supply and all power supplies, at the very least, have a voltage rating. A voltage rating is an indication of the nominal voltage that a power supply will provide

For example, most car batteries are rated at 12 volts (V), which is the nominal voltage. If you have a voltmeter, try and measure your car battery voltage, and you will realise that it’s not exactly 12, it is usually higher. It similar with the voltage at your home, if you live in Australia, the nominal voltage is 230V but the measurement can be anywhere between 220 to 250V

Every electrical equipment that you see around you would need a specific voltage and it will only work reliably at that voltage. That’s why, to understand any circuit, you need to know the supply voltage.

But you can’t stop there; you need more specifications of the power supply if you intend to have a robust system. Here are some more specs and their examples

Rating Example
Ampere-hour
You will see this rating on batteries. The amp-hour rating is also called battery capacity and can show how long a battery may last
Power rating
Some power supplies like solar panels will have ratings that end with W, which stands for Watts. That’s the maximum power it can provide
Current rating
Power supplies like your phone chargers also give you a current rating, which is the maximum current it can provide when charging your phone battery

All circuits are designed to do something

The purpose of any circuit is to do something for us. For example, a lighting circuit at your home is supposed to give you light. All electrical or electronic devices that use electrical energy and provide another form of energy in return are loads.

Here are some examples of loads

Realistically, everything is an electrical circuit consumes electricity, some more than other and most intentionally and some unintentionally. You may have noticed that the coils in some heaters light up orange when turned on. That is light energy, but do you expect to get a light from the heater? Perhaps as an indication of operation but not practically useful.

Similar to this, each component in a circuit may be using the electricity in ways that we don’t expect. However, we only consider a device as a load only if we intend to get something out of it.

You need to be in control

In any electrical or electronic circuit, there needs to be a way to turn the load ON or OFF, at the very least. This is the job of a control device. There are many types of control devices, but the most basic one is a switch, like a light switch.

Here are some examples of control devices

Practical circuits have many control devices, and some devices can control the load in a few different ways. For example, you may have noticed that some houses have lights on the outside that turn on when there is some movement, which works using a Passive Infrared (PIR) proximity sensor. In most cases, these sensors will also have a switch, which will disable them and keep the lights off to save power during daytime.

The lights, along with the PIR and switch will be a part of a larger circuit that will be controlled by a circuit breaker. And the current to this circuit breaker will come from the main circuit breaker. There are more control devices even before these. The circuit breakers serve a dual purpose, circuit control as well as circuit safety, but we will discuss that in another topic.

In some cases, there may not be a control device physically present, where the load is connected directly to the power supply. In these situations, the points where the wires connect to the supply terminals act like control devices. So, if you physically disconnect the wire, the load will disconnect from the circuit.

What's the right path

When you want to connect a load to a power supply, you will need a path that will allow the current to flow itself. The materials that allow the current to flow easily are considered good conductors of electricity. There are varying degrees of conductors, for instance, a copper wire is a better conductor of electricity than aluminium, but both materials are conductors.

Here are some conductors with an example of their applications.

Rating Example
Silver
Silver is perhaps the best conductor of electricity. It’s quite widely used in contacts of switches
Copper
Copper is the most widely used conductor in the electrical and electronics industries. The cables used in house wiring a copper
Aluminium
Aluminium less conductive than copper but is used in power lines because its lightweight
Gold
Gold isn’t as good as copper for conducting electricity, but it doesn’t rust easily. Many connectors have gold contacts.

Insulators

As opposed to conductors, some materials do not allow the current to flow through themselves – these are called insulators. Insulators aren’t necessary for a circuit operation but are essential for the safety of the circuit and people.

For example, thermoplastic sheathed (TPS) cables are probably the most widely used cables in installation wiring in Australia. The plastic sheath is the insulator, and inside it, there are copper wires, which are the conductors. The insulator stops access to the conductors that will carry current.

Some of the most popular insulators are plastic, rubber, paper, etc.

Conclusion

We just looked at the four most essential parts of an electrical circuit. If any one of these is missing, the circuit isn’t complete and won’t work as expected, if it worked at all.

This doesn’t mean that no other types of parts are used in circuits. There are a few other types of components that can make the electrical circuits safer, more reliable and easier to maintain or troubleshoot. These are called additional circuit components like circuit breakers, fuses, meters, etc. but we will discuss these in another post.

I hope this post helped you understand the basic building blocks of a simple electrical circuit. Please feel free to leave a comment if you would like to add to the information in this post.

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About the Author

Husnen Rupani

Husnen Rupani

I help electrical training organisations increase learner engagement by designing innovative training equipment. I have a saying "Electricity - you cannot see, you cannot hear it, but by the time you feel it, it may be too late." My main aim is to turn this black magic that we call electricity into something that people can understand.

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