Static Electricity

Static Electricity occurs in nature

Electricity

Form of energy and can be converted to other forms of energy

Take electricity for granted – where does it come from?

Discovered by a Greek philosopher 600BC.

Objects like a plastic biro, a polythene rod, or a perspex rod etc.. become charged when rubbed with a woollen

cloth or other materials.

They can then attract small pieces of paper. The rubbed materials are charged with

STATIC ELECTRICITY.

Experiment: Demonstrate the production of static elecricity by friction

Method: 1. Rub a plastic biro in your hair or your jumper. 2. Hold it near some small pieces of paper

Result & conclusion: The paper is attracted to the biro due to staic electricity on the plastic biro

“Static electricity involves electric charges that collect in one place and remain

stationary.”

STATIC ELECTRICITY is electricity that does not move. It is a build-up of electric charge and can be produced by friction

Charging by friction (rubbing)

Bodies become charged by the gain or loss of electrons a body is +vely charged if it loses electrons. A body is –vely charged if it gains electrons.

The charge that moves is the negative charge, i.e. the electron which is the smaller and freer particle in the atom

If a polythene rod is rubbed with a woollen cloth, a transfer of electrons takes place.

Friction (rubbing) causes some of the outer electrons of the wool to escape. These get transferred to the polythene rod.

The rod has now gained electrons and is negatively charged.

The wool has lost electrons. It now has more protons than electrons and is positively charged.

Charging rods positively & negatively

Wool Lost electrons Now + vely charged Polythene Rod

Gained electrons Now – vely charged

+ + + + + + + + +

Friction caused by rubbing the polythene rod with the cloth removes electrons from the cloth giving it a negative charge as electrons are negative

A perspex rod is now rubbed against the woollen cloth. The energy produced by the friction sets some of the electrons free.

These electrons are transferred to the wool cloth.

The perspex rod ends up being positively charged as it has lost electrons.

The wool cloth ends up being negatively charged as it has gained electrons

Charging rods positively & negatively

Wool Gained electrons Now - vely charged Perspex Rod

Lost electrons Now + vely charged

- - -

- - - - - -

Friction caused by rubbing the perspex rod with the cloth removes electrons from the rod giving the rod a positive charge and the cloth a negative charge

Like Charges repel each other

Unlike charges attract.

Charged bodies are said to have static electricity

Experiment: Show that like charges repel

Method: 1. Suspend a negatively charged polythene rod from a retort stand using some thread. 2. Bring another negatively charged polythene rod near it.

Result & conclusion: The suspended rd will

move away. Therefore, like charges repel.

Experiment: Show that unlike charges attract

Method: 1. Suspend a negatively charged polythene rod from a retort stand using some thread. 2. Bring a positive Perspex rod close to the negative rod.

Result & conclusion: The rods will be seen

to attract. Therefore, unlike chages attract.

Earthing As stated earlier, STATIC ELECTRICITY

is due to electric charges that remain at rest on an object. These charges cannot move.

This is because the material on which they stand are INSULATORS.

“Insulators are substances which do not allow electric charge to flow through them easily.”

Examples of insulators: polythene and perspex rods, glass, plastic, rubber.

Insulators Substances like plastic and rubber

are electrical insulators. This means that they don’t allow charges to flow through them easily.

A conductor is a substance that allows electric charge to flow through it freely

eg. metals.

Earthing A plastic rod is a good insulator, it can build

up and store quite a large amount of electric charge.

This charge will remain on the insulator for a long time. It has no route to go away.

However if a conductor touches the charged plastic rod, things change.

The conductor becomes the escape route for the build up charge.

An escape route for this electricity is called the earth connection.

Charge moves from an object where there is a surplus of charge to a neutral object like the earth through a conductor.

“Earthing means connecting an object to the earth using a conductor so that the object

loses its charge to the earth.”

While an object is earthed a charge cannot build up in it.

Earthing

We say an object has been “earthed” when an object has lost its charge to the earth.

Person getting shock from touching wire, door handle (metal).

By walking on nylon carpet with rubber soled shoes, you can easily build up static charge on your body. this static electricity has no easy way to flow to the earth unless you touch something made of metal. You feel a shock as the charge jumps to the metal and flows away to the earth.

The earth acts as a sink for charge

Other examples of static electricity

Lightning is caused by static electricity building up in the clouds.

The amount of charge builds up until eventually the cloud earths itself by sparking to the ground or to a nearby cloud.