 How do you heat things up? Well one way is to apply light radiation to them, just like we've seen here. The old electric field pulls the charges around and makes things hotter. That's why you get warm on a summer's day. Another way is to put your object in something hotter. So let's say for example you put a baked potato in a campfire. The atoms in the baked potato are moving slowly, so they're not rotating very much, they're not vibrating very much, the springs are not very much stretched, there's low energy in all those forms. But what's going to happen when it's in the fire is the air around it is very hot. So the very hot air molecules are going to be spinning like crazy and bouncing and vibrating and running around like crazy. We'll smash into the molecules on the outer parts of the baked potato. And of course if you're a slow moving atom and a fast moving atom bashes into you, it's going to get you moving faster. And so first of all the molecules on the outside will start moving faster and because they're attached with bonds to the ones on the inside, it'll pull the inner ones moving faster and slowly over time all the molecules will go faster and your baked potato will cook. That's very similar to what happens here when you have a stove, you're cooking something with fire underneath, the very fast moving molecules down here will bash into the bottom of the pan and get the molecules in the pan moving really fast. The molecules in the bottom of the pan are attached to the ones in the top of the pan so the whole pan will warm up and that will then heat up whatever's inside it. Another way to apply heat is with electricity. If you have an electric kettle like this one, it'll have a heating element somewhere at the bottom which is basically a piece of wire. So you have a piece of wire and an electric field is applied along it by your mains and that means electrons will start accelerating along it. As they accelerate along they'll bump into atoms and they'll make the atoms jiggle. The electron will then bounce off but then the electric field, the voltage will cause it to accelerate again and that will cause another one and cause that to jiggle. So there'll be some sort of resisting element inside with electrons being accelerated through by the voltage and that will cause the atoms in that to jiggle faster and faster and faster and the fast jiggling molecules in the wire will then bounce off the molecules in the water around it and cause them to go faster and before long you've got a nice hot cup of tea.