Hello Lauren,
I don't know how complicated an explanation you need, so I will keep it simple.
The flashlight is really a simple device. It consists of one or more batteries,
a switch, a small light bulb with a reflector to focus the light and a "body" to hold everything.
If there is more than one battery they are usually connected in series. This means one battery is behind the other and it's positive terminal is connected to the second battery's negative terminal. When we put the batteries "end to end" like this we get two times the voltage of a single battery. What we are doing is "adding" the electricity together. We can put as many batteries as we want end to end to add electricity. If the batteries are common ones, each one is 1.5 volts. Two end to end will make 3 volts, get it?. The more volts we have the brighter the light will be. There is more to it than that but I'm keeping this simple.
It looks like this:
________________________*switch*_____
************************ *
* ------- ------- --*- >>>
* *-#1bat+**-#2bat +****** bulb >>> light
* ------- ------- ---- >>>
*____________________________________
All the "*" are the little paths the electricity must follow to get to the light bulb. You see, the body of the flashlight is usually metal and is connected to battery number 1. In order to make the light bulb light, we must connect both sides of our two batteries to it because electricity needs to leave one battery and come back to the other.
All electrical circuits need to go around in this "circle" to make something work. The switch stops the body of the flashlight (which is also the negative from battery # 1)from connecting to the bulb unitl it is pressed and then the complete circle in the circuit is made.
This is OK to hold in your hand because the electricity is too small to shock you and you are not touching the other end of battery # 2 so no circle is made through you.
The light bulb has a little wire inside called a "filament". This little wire gets very hot when electricity goes through it. It's like your toaster at home, but it gets much hotter. So hot, it glows and makes light. The light kind of spreads out so we need to focus it forward to where we want it.
The reflector does this. It "collects" the light and sends it out the front of the flashlight in a nice beam. (lol...well, sometimes.
When things get very hot they will burn up, but all the air has been sucked out of the light bulb and the little filamnet can't burn up without the oxygen thats in the air.
Sometimes special gas is put inside the light bulb to make it brighter too.
Oygen is a funny thing. We all need it to breathe or we would die, but it also makes things burn and even makes things like steel rusty. It makes your food go bad and does many other bad things, but life couldn't exist without it. It just shows that God has a sense of humor
Also, the filament is made of a special metal that can get real hot without melting.
It's called "tungsten" and it's the highest melting temperature metal known.
So you see, the batteries have chemicals inside them that make electricity when there is a closed circle to the light bulb. These chemicals get used up and eventually the batteries go dead. We are just changing chemical energy into electrical energy and then into heat and light energy. We can change the energy we have into many different forms.
The best way to see how a flashlight (or anything else) works is to take one apart and study it. If you get two wires and connect the battery to the light bulb you will have a closed circuit and the bulb will light up. (This can't hurt you if you do it as long as you use common batteries.)
Just remember that all electricity must leave the place it is made and come back to it after it does the work you want it to do, in this case heating up the little filament.
There must be a "closed" path so it can get back. (Even the electricity that leaves your house ends up back at the place that made it.)
I hope this helps. If you have more questions we will be happy to asnswer them. Good luck with your flashlight project.
