AQA additional physics GCSE - Static Electricity P2 4

When two electrical insulators are rubbed together the electrons are rubbes of one material and onto the other.

Electrons have a negative charge so the material gaining elecrons becomes negativly charges. The one that has lost electrons become positvly charge.

Like charges repel, unlike attract.

The bigger the distance between the objects the weaker the force.

Electric charge is the rate of flow of charge.

Metals are good conductors because they contain free electrons that are not confined to one single atom.

Insulators cannot because the electrons are held by atoms and are not free.

A conductor can only hold charge is it is isolated from the ground. Otherwise electrons will flow to or from the earth.

The bigger the charge on an isolates object (conductor) the higher the potential differerence. If the potential difference becomes high enough a spark may jump between the object and any earthed conductor near.

Uses

Objects such as car panels and bike frames are painted with an electrostatic paint sprayer. The nozzel is conected +. As the paint passes through it they pick up the +charge. The paint drops repel each other (because likes repel) and spread out to form a fine cloud. The item being painted on is conected -, and this is why the paint sticks (because unlikes attract).

Electrostatic smoke precipitatios are used in chimmeny's to attract dust and smoke particles so tey do nor release into the air. The particles pass a charges grid and pick up the charge. They are then attracted to the plates on the chimmney walls that have the opposite charge. The particles stick here untill shaken off.

Dangers

When a powder or grain flows through a pipe friction makes it pick up charge. This could lead to a spark igniting the powder and causing an explosion.

The filler pipes on road truckers that are used to pump fuel into storage tanks are earthes to prevent them becoming charged. A spark could cause nd exploion of the fuel vapour.