Physics

Physics - Unit 2Static electricityFrictionnnn charges which are unable to move build up in one place- causing a static shock or spark. When two insulating layers ( such as a polythene rod and a cloth) rub together, the electrons are transferred from one to the other - changing charges. This means that one will have a positive static charge and one will have a negative static charge. The electrons are passed between each other- because electrons are negatively charged, the material which has less electrons will be positively charged .

An atom contains a nucleus - this is tinyyy but makes up most of the mass of an atom. It contains protons ( with a + charge) and neutrons which have a neutral charge. The rest of the atom is mostly empty space in which electrons ( with a - charge) spin around in shells. The have a mass of 1/1836 so it's virtually nothing...

Examples of static electricity Clothing - when taking off a jumper you may find that your hair sticks on end. That's because the electrons are transferred from one to the other leaving one positive and one negative. Attraction occurs. Sparks may happen as the charges try to rearrange themselves. Car shocks - Static charges can build between clothes and a synthetic car seat. Then when you touch the metal door ( in which the charge flows) you can get a shock. Conducting strips hang down off some cars which gives a safe discharge to the earth and stops there from being any danger. Shocks from door handles work in the same way. If you walk on a nylon carpet with insulating shoes then touch a metal door handle the charge flows and you get a shock. Balloons stick to walls when they're rubbed against it or against hair because the negative charge on the balloon pushes away the negative charges on the way and attracts the positive charges. This is called induction. A charged comb can pick up pieces of paper in the same way. The comb can be charged by running it through your hair. Lightning is caused by a build up of static charge.

Uses- Paint sprayers- the spray gun is charged which charges the paint droplets. Because they're all the same charge, the paint droplets repel each other so there's a very fine spray of paint. The object will be given an opposite charge therefore, when the paint is sprayed, the coat will be even as the oppositely charged particles attract. Even parts of the object which are faced away, or tucked behind small crevices will gain an even coat of paint.

Dangers -As fuel flows from a filler pipe into an aircraft tank or car the static charges can build up. This can easily create a spark which could create an explosion in a dusty or fumey place like a petrol station. It is therefore important that we "ground" the charge or "earth" it. By earthing charged objects this means that we can stop an explosion from happening.

How do we earth objects? A conductor is placed from the charged object to the ground ( for example a copper wire may be used). This provides a route for the charges to travel into the ground so therefore a static charge cannot build up. The electrons travel down the conductor into the ground if the charge is negative. If the objects charge is positive then the electrons flow up from the ground. This prevents any sparks from being created or any explosions.