HOW ELECTRICITY WORKS: PART 1

The other day, a friend of mine was talking about how difficult it had been to understand or describe electricity and how it works.

I went a bit red. Even with a degree in physics I didn't really think I'd be able to help, as for me, the same mental blocks had kicked in early on, and I remembered what that felt like. What's impedance? Why don't I understand what voltage is? What's DC? What's AC? If I switch the plug socket on is it constantly on, or does electricity only work when something is plugged into it? Am I really stupid for not understanding it? It was a big issue for me.

So I had a think, and I reckon I've come up with a nifty analogy. This would have been useful to me, when I needed to know it - but I don't remember the text books being all that helpful. So, here's me reminding myself how electricity works, written as I would have liked it aged 13. We'll call it part 1.

---

How Electricity Works - Part 1

You can think of electricity as water to help you understand what might be happening in an electrical circuit. That's an okay comparison because electricity is really just a flow of tiny charged particles. They flow, they move, they sweep downstream and they do stuff. So let's start there...

Current (I) - Current is a measure of how fast the electricity is flowing, just like a flow-rate tells you the speed of a river or stream. The unit of measuring electrical current is the Ampere or Amp for short. A high current means the flow is moving faster.

Voltage (V) - this is a bit like the water pressure, or a measure of how much energy the flow carries in a certain volume of water. Voltage is measured in Volts. The higher the voltage, the faster the flow - just as a river flows faster if the hill is steeper, or is being pumped by something upstream.

Resistance (R) - this is a measure of how good a particular material is at stopping or reducing the flow. For example, a sponge is a really good resistor: it slows down the current, and it reduces the pressure. High resistance means a lower current.

Also, the size of the water-pipe might affect how much water can flow through it at any one time. So a smaller pipe lets less water through per second than a wider one will. The smaller the pipe, the greater the resistance. Electrical Resistance is measured in Ohms.

Ohm's Law

Ohm was a German physicist who worked out exactly how resistance affects the flow of electricity: "Ohm's law" tells you how current, voltage and resistance work together.

For example:

Imagine you have a tank of water with a pipe or a hose attached to it.

If you increase the water-pressure in the tank, the speed at which it spurts out of the pipe goes up, just like squeezing a lemonade bottle or a tube of toothpaste. You could increase the pressure in the tank by forcing the water out so that it's got nowhere else to go but through the hosepipe! What happens to the current (how fast the flow is) when the pressure goes up?

This is Ohm's law. It states that the current is faster when the voltage is high and the resistance is low. Or, the opposite: that the flow is slower when either the resistance is high or the voltage is low. It's usually written like this:

V = I x R

Circuits

A circuit is a complete system, usually with a 'load' in it, for example, a water wheel or a light bulb. The load is the bit that moves or lights up or does something as a result of the flow. Loads are the useful bit.

You can measure how much energy is produced by a system, by watching the load. Water-wheels used to turn machinery that ground flour in old mills. If the river flooded upstream and it moved faster, the wheel turned more quickly and generated more power. If there was a drought and the river slowed down or stopped, it was bad news for the miller and everyone who liked bread. The power of the system depended on the current.

A higher flow of electricity (current), or a greater pressure (voltage) generates more energy for whatever load the circuit is powering. Similarly to a water-wheel in a river, a light bulb in a circuit gets brighter as the amount of power increases.

Power is directly related to how much voltage (pressure) there is, and how fast the current is flowing. Power (W) is measured in Watts.

W = V x I

Power is the product of the voltage and the current of a system. You might notice that light bulbs have a rating that's measured in Watts. That's a direct indication of how much energy they use, and therefore how bright they are when you plug them in.

So, the more energy you have, the brighter you can be. That's why you should eat good food, by the way.

---

Would that have helped? Does it make sense? Is it even right? It's probably obvious, but it was worth a go. I reckon in Part 2, I could talk about AC and DC and maybe even a bit more about how those mysterious electrons carry charge, and why.

Though obviously I'll have to figure it out first.