You put a piece of paper in, you push a button, an exact copy of that paper comes out. How does that happen? Thank the laws of electrostatics. Also, it's worth noting that photocopier toner (the black stuff that actually makes the marks) is a mixture of powdered carbon and microscopic particles of plastic, which melt when exposed to heat. That's how the toner sticks to the paper. Laser printers work in a very similar way, except a laser is responsible for "painting" a charge on the drum for a laser printer.
It's not the most exciting device, but its ability to take small dust particles out of the air, such as in the smokestack of a coal-burning power plant, make it very useful. Dust particles, which are neutral, are forced through some very highly charged metal plates. As we have seen, neutral particles are attracted to charged objects: the dust is taken out of the air before the smoke escapes. There are even some home-heating furnaces that use this to purify the air that it heats, although they do have some drawbacks, such as being difficult to clean.
If you're a company that needs to spray-paint a lot of objects, such as a car manufacturer, you want to save money and do a good job. Like with the precipitator, we can use the laws of electrostatics to help charged and neutral objects stick to each other. The difference here is that droplets of paint can be given a charge, which will be attracted to a neutral object, which is grounded. The following video gets a little technical at times (it's made by a company that makes spray-painting systems), but it covers a lot of the basic ideas.
This short video (also made for a painting-equipment company) shows how well this works. As you can see, it works very well! Hold on until the end to see how well this works.
Be careful with this at-home experiment... as you can see early on, you can make a device that can give you quite an electric shock if you're not careful. A capacitor is an electrical device that can store electrical energy for a short time. It's a little like a battery or a cell, but it can discharge that energy very quickly in the right situation. (This video never uses the word "capacitor," but that's really what a Leyden Jar is.)