P2a Topic 1 - Static and Current Electricity Flashcards
The nucleus contains protons (which are positively charged) and neutrons (which are neutral) - this gives the nucleus
An overall positive charge
What are the relative masses and charges of each atomic particle
1) proton - mass of 1 - charge of +1
2) Neutron - mass of 1 - charge of 0
3) Electron - mass of 1/2000 - charge of -1
Build up of static is caused by
Friction
When two ____________ materials are rubbed together, ____________ will be scraped off one and dumped on the other.
Insulating, electrons
With the polythene rod, electrons move from the duster to the rod. The rod becomes ______________ charged and the duster is left with an equal ____________ charge.
Negatively, positive
With the acetate rod, electrons move from the rod to the duster. The duster becomes _____________ charged and the rod is left with an equal ____________ charge.
Negatively, positive
Like charges
Repel
Unlike charges
Attract
Explain how clothing crackles occur
When synthetic clothes are dragged over each other (like in a tumble drier or over your head), electrons are scraped off, leaving static charges on both parts. This leads to the charges attracting and little sparks as the charges rearrange themselves.
Explain how car shocks occur
Static charge can build up between your clothes and a synthetic car seat - the friction between the two causes electrons to be scraped off. Then, when you get out of the car and touch the metal door, the charge flows and it can give you a real “buzz”. Some cars have conducting strips which hang down behind the car to provide a safe discharge to earth.
Explain how you can get shocks from door handles
If you walk on a nylon carpet wearing shoes with insulating soles, there will be a transfer of electrons from the carpet to you and charge will build up in your body. Then if you touch a metal door handle, the charge flows to the conductor and you get a little shock.
Explain how balloons can stick to walls
Rubbing a balloon against your hair or clothes causes electrons to be transferred to the balloon, leaving it with a negative charge. If you then hold it up against a wall it will stick, even though the wall isn’t charged. That’s because the charges on the surface of the wall can move a little - the negative charges on the balloon rebel the negative charges on the surface of the wall. This leaves a positive charge on the surface, which attracts the negatively charged balloons - this attraction holds the balloon on the wall. This method of using a charged object to force charges in an uncharged to move is called induction.
Explain how a charged comb can pick up small pieces of paper
If you run a comb through your hair, electrons will be transferred to the comb and it will become negatively charged. It can then be used to pick up little pieces of paper, even though they have no charge - holding it near the little pieces of paper causes induction in the paper, meaning they will stick to the comb.
Explain how lighting is caused by a build up of static charge
Rain drops and ice bump together inside storm clouds, knocking off electrons and leaving the top of the cloud positively charged and the bottom of the cloud negative. This creates a huge voltage and a big spark.
Explain how paint sprayers can use electrostatic charges
The spray gun is charged, which charges up every drop of paint. Each paint drop repels all the others, since they’ve all got the same charge, so you get a very fine spray. The object to be painted is given an opposite charge to the gun. This means the paint is attracted. This method gives an even coat and hardly any paint is wasted. In addition, parts of the object pointing away from the gun still receive paint i.e. there is no paint shadows. Many electrostatic sprayers work in the same way e.g. insecticide sprayers.
