Electricity- Charges and static electricity

Storm clouds contain ice particles. These ice particles rub against each other and lose electrons. As the particles lose electrons they become charged. These charged ice particles accumulate and develop huge areas of charge within the cloud. The charge in these areas builds up until it eventually discharges into other areas of opposite charge or to the ground. As the charges move through the air they heat the air molecules causing the air to glow(lightning). As the air heats up it expands and creates the mighty roar of thunder that we hear after every lightning bolt.

Static electricity
There are two forms of electricity, static and flowing. Static electricity is familiar to all of us and can be quite a nuisance. Walking on carpet can sometimes give you a small shock when you touch someone else or a metallic object. The Van de Graaff generator is familiar to most of us and is used in many classrooms to demonstrate build up of static electricity.
Static electricity occurs when electrons build up on the surface of insulators. Only insulators and insulated metal, can develop a buildup of charge. Unlike metals, insulators can not conduct the buildup of charge away from the source. Electrons(negative charges) build up until they start to repel each other and no more can deposit due to electrostatic forces of repulsion. The build up of charge is under immense electrical pressure and quickly flows to areas of low pressure, such as the ground, when another object connected to the ground is brought close. Look at the animation on the right. Charge is built up by rubbing certain materials together. Electrons are forced off one material onto the other. In the case of the Van de Graaff generator electrons from a cloth are transferred onto the insulated metal head. Charge quickly flows, in spectacular fashion, when a neutral rod connected to the ground is brought close.		Click to see a 120kb movie of how the Van de Graaff generator works. Notice the movement of charge when the generator is discharged.
	We can demonstrate a buildup of charge using a Van De Graaff generator. Look at the video on the left. When a rod connected to the earth is brought close to the charged metal dome a spark is produced as charge discharges through the air to the earthed object.
	Lightning occurs when static charges in the clouds flow to other clouds or to the ground.
Storm clouds contain ice particles. These ice particles rub against each other and lose electrons. As the particles lose electrons they become charged. These charged ice particles accumulate and develop huge areas of charge within the cloud. The charge in these areas builds up until it eventually discharges into other areas of opposite charge or to the ground. As the charges move through the air they heat the air molecules causing the air to glow(lightning). As the air heats up it expands and creates the mighty roar of thunder that we hear after every lightning bolt.
	You can have a great deal of fun using a Van De Graaff generator. Tape tissue papers to the generator or place a small pile of tissues on the top. Charge the generator and observe what happens. Long tissue papers look spectacular as the generator is being charged.

Construct a vicious octopus by using a Van de Graaff generator with long strips of tissue paper attached to the dome, as shown on the right. When charged, the tissue papers rise and move away from each other. Why?
Why do the tissue papers collapse when the generator is discharged?
When the earthing rod is brought close, the tissue papers appear to be attacking the rod. View the video on the right. Why do the tissue papers become attracted to the hand. What charge is the hand? What can you say about neutral and charged objects when they come close to each other? Hint
Activity - Static electricity