A torch works through a conducting part, a reflecting part and a circuit made up of a set of cells. Find out how light is reflected in a torch with information from a science teacher in this free video on physical science lessons.
Hi, I'm Steve Jones and I'm going to explain how a torch works. Well, I've got a diagram here of a torch. If I draw the circuit as a circuit, a battery, remember a battery is the word for a group of cells. A battery, the word battery just means a group. So, it's a battery of cells. So this is a battery and we've got here three one half volt cells, so you've got four point five volts. There are three cells in series, inside the body of the torch. At this end you can see there is a bulb. This is a filament lamp, that is it's got the small thin piece of metal inside which gets hot which provides the light. It's got a screw thread which attaches it to this side part here and this is part of the conducting part of the torch. So we end up with a circuit that looks like this. We have a switch which we see here and we have a lamp. Now this is a filament lamp usually represented in this way. And that is our circuit. It's fairly simple. It's a cell or set of cells, a switch, and a lamp. Here the electricity will travel through the filament, there's the filament inside. So it comes in around the filament and it comes in on this bottom part here which connects to the cell. So the circuit is shown by, there's the switch, there's the lamp and here's the cells and that is the circuit. The additional thing that we find is next to the bulb there is a reflecting part, a reflector here, to reflect the light this way and at the front a plastic lens. This completes the torch. And obviously my torches never work and usually the reason is I don't use them very much. These batteries will run down very quickly if they're not actually used. So remember that's how it works, so look after it and then it'll work when you want it to.