Roadwolf's Electronics Series: Part 2, Static Electricity
Static Electricity is likely the most common form of electricity on the planet, and in the whole universe and all of existence. In our everyday lives it is often caused by mechanical friction. Weather you are walking across a plush carper in stiff soled shoes or slippers, or you are drying clothes in the dryer. Mechanical friction causes these surfaces to exchange electrons.
A good experiment on a dry day would be to use a plastic comb, and run it through your hair. It will remove electrons from your hair, and become negatively charged. Likewise you can take a glass rod, and rub it with a silk cloth. It will become positively charged. Both of which will be able to attract small slivers of paper. Many materials will be able to be charged by rubbing them with a non conductive and material. Metal will not work in this manner, as it allows the electrons to travel inside the metal, and they will quickly be leaked away.
So how do we know that the comb and glass rod have positive and negative charges? A founding rule of electricity is that like charges repel each other, and unlike charges attract each other. A fun and simple way to test objects is to use fishing line and tie small foam packing chips, hanging them near each other. If you hold the comb up between the foam chips, you will see that the chips try to move away from each other. However if you hold the glass rod up behind one chip, and hold the comb up behind the other chip, you will see that they will attract towards each other.
This is useful in designing a simple 'Electroscope'. The Electroscope, is a simple device which consists of a thin piece of folder foil, hung on a wire, which is then used as a probe to test for static electricity. If static electricity is present, no matter if it is positively or negatively charged, it will cause the foil to fly apart. You can use this to test what is conductive or not conductive, as you can connect various types of wire or other objects to it, and then apply a known static charge.
This is a good way to determine the difference between conductors and insulators.
Conductors include: Metals like Silver, Iron, Copper, Gold, Aluminum, Tin, Lead, and to some extent, Carbon.
Insulators include: Glass, Plastic, Rubber, Wood, Ceramic, and even most organic oils.