Current describes the flow of electricity. Think of current as something like the water that passes through a hose – we can think of current as something like the flow of electricity through a conductor.
A conductor is some material through which a current can flow.
Every conductor has a certain level of resistance to that current.
Think of a river with that has many rocks that resist the flow (the current) of the water.
As a conductor resists current it heats up because its pushing against and being pushed by the current. This is why an old fashioned light bulb lights up…it has a conductor designed to glow white hot by resisting the flow of electricity.
But what pushes the current through all this resistance?
Voltage. Voltage might be thought as the amount of force that causes the current. It is the most important of these terms. With a voltage there can be no current.
Voltage is also described as ‘potential difference’ which sounds even more complicated. Think about a dam or lake on top of a mountain full of water. The water wants (has the potential to) flow because of the height difference between the dam and the valley. The more water and the more pressure there is to flow; If the valley filled up with water there would be no difference between the dam and the valley and there would be no potential for flow.
We can think of a battery as operating something like this dam. The positive terminal is the mountain top and the negative is the valley ground. If we connect them together with a conductor the difference between them will push a current from one side to the next until both sides are equal. At this point the battery has no voltage and so no more current will flow.
Voltage is what makes electricity potentially dangerous. Electricity always wants to travel to ‘ground’. That is what we see when we see lightning ‘hitting’ the ground – we are seeing a potential difference between the cloud and the ground get so large that the resistance in the air is no longer enough to stop a circuit forming and a current passes from the cloud to the ground.
The resistance in the air is so great that the air itself heats up and burns – because even that resistance is not enough to stop the current flowing because of the huge voltages that have developed between the cloud and ground. This is why we see a light and here a crack of thunder.
Our bodies are poor conductors of electricity – but they do conduct. If we touch a positive and a negative terminal at the same time and the voltage is great enough to push a current through our resistant bodies we will get an electric shock.
At Polygon Door we never connect anything we are making to the power at the wall. This is because that wall sockets has a Voltage of 240 Volts – more than enough difference to give youa dangerous shock.
In the Pablo Kit we use a battery with the to deliver high current relative to its relatively low voltage. This means we should be careful about short circuiting this battery (and batteries generally). Normally small batteries don’t have the required voltage to push a current through your quite resistant body – but don’;t try it with this battery.
If you have a simple 9v battery available instead (the square type used in toys) you can touch your tongue to both negative a positive terminals at once and you will feel a current produced between the two terminals because your spit offers less resistance across the surface of you skin and a current is produced.
When a current flows between the two terminal the battery is discharging (losing the difference between the two terminals) and will eventually have no charge left.
If we connect two terminals with a wire the amount of current is so great it produces a large amount of heat due to the resistance it meets in the wire. This is called a short circuit – and either the battery will discharge or the current will produce to much heat in the wire cause the wire to burn or melt.
We never want to to be that wire! So lets keep our fingers away from large voltages.