Tutorial electric circuit

If you want to know a bit more about what exactly an electrical circuit is, or what the ‘current, voltage and power’  that the multimeter shows actually means, then you should definitely read this explanation. It can get a bit technical from time to time, but try to experiment as much which these concepts as possible and you will quickly start to understand what it’s all about.

Circuit
The most important thing to know is what an electrical circuit (or also called network) actually is. It is just the combination of all the electrical pieces that you connect with eachother. A simple example of a circuit can be seen in the picture. But even a single cable all by itself forms an electrical circuit (although it’s not a really useful circuit).

For a circuit to work, there are 3 crucial components: generators, cables and consumers.

The generator is what powers everything. Normally it requires some sort of fuel which it uses to create power and electricity. When your system is not doing anything, it is probably because the generator is not working as it should. Unfortunately a generator cannot create an endless amount of power but there is a limit. If you require more power from the generator than it can provide, then you will see that your consumers will not work the way they should. Cables are like the pipes across which the electricity can flow. They bring the power from the generators and make sure it arrives at the consumers. Cables let electricity flow in any direction and will automaticly connect to everything around them that they can connect to, so there is no need to worry about how you should place them.

The third essential element are the consumers. They can be lamps (as shown in the picture), but they could also be furnaces, special doors, elevators ... They only need to require some sort of electric power before they are seen as consumers. And this electrical power should be provided by generators and then brought to them by using cables. Every consumer requires a certain amount of power before it will work as it should. For example, if a lamp receives less power, it will nog longer shine as bright as it did when it received all the power it needed. Adding more consumers to a certain network will increase the amount of power that the generator delivers, untill it gets to its limit. Physical background

Current
Electricity consist of electrons (which are tiny charged particles) that move around in the cables. The number of electrons that flows through a machine is indicated by the current flowing through that device. This current of electrons (or just current for short) is usually expressed in Ampère.

Voltage


Now, why would these electrons want to move from one place to another? This is because the generator ‘pushes’ them from one side to another. How hard the electrons get pushed is expressed by the difference in voltage. They get pushed from a place that has a high voltage to a place with a low voltage. Compare it with water flowing down or a ball rolling of a hill. The higher this voltage difference is, the harder the electrons will be pushed and the faster the current will be. When using voltmeters or multimeters in this mod, the voltage that is given by these devices is always compared to that of the ground (which is defined as zero), where all the electrons finally end up.

Resistance
Unfortunately, these electrons can’t flow freely through the devices. All these devices have a certain resistance. This is how good the voltage difference can push the electrons though the cables to create a current. Mathematically it is defined as Voltage=Current x Resistance. So a cable that has a low resistance will have a big current flowing through it at a certain voltage.



Water comparison


A useful comparison to explain these concepts is that of water flowing through some pipes. In that situation water flows from one container to other because there is a height difference between certain containers (the voltage or potential difference). The current is just the flow of water through a pipe (which is analogous to a cable). Pipes also have a sort of resistance, for example bigger pipes will allow more water to flow through them so they have a lower resistance.

In this water analogy a generator is then similar to a pump that brings water from a low point (the ground) to a higher point (a certain voltage) so that it can flow downwards again, powering things like waterwheels.



Power
Although this is all very nice, it doesn’t really tell what a certain consumer/generator can use/produce. Or in other words how much power it consumes or generates. This power depends on two things: the current flowing through the device and how hard it is being pushed, so on the voltage. This comes down to the power being given by Power=Voltage x Current which is also equal to Voltage²/Resistance and it is usually expressed in Watt. So a device that uses more power will require a bigger power supply, which your generators should then produce.

This second formula also means that every device that has a resistance will produce a certain amount of power, including cables. Although cables do not produce anything useful, they still consume power and turn it into heat, which is energy that just disappears. That is why cables will be the biggest reason for energy losses in an electric network. When really long cables are used, there will be such a big loss of power on them, that is it possible that the consumers at the end of the line do net receive enough power to function properly. There is another, more dangerous consequence of the heat production of cables, being that if the current that flows through a cable becomes too big, it could overheat and start burning or even explode. That is the reason why all real households should have some sort of fuses.