Static Charge

What does static charge mean?

Static charge refers to electric charge that can be held in one place (aka static electricity)

What are examples of static electricity?

• A lightning strike

• Dusters that attract dust

• Crackles when combing hair

• Plastic wrap sticking to your hands

• Dust being attracted to television screens

• Clothes clinging to each other in a dryer

• Getting a shock after rubbing your feet on a carpet and then touching a metal object

Where does static charge come from?

All materials are made of atoms, which contain electric charges

There are electrons around the atom, which are negative

There are protons in the centre of an atom, which are positive

An atom has an equal amounts of positive and negative charges, so the atom had no overall charge

Electrons do not always stay attached to atoms and can sometimes be removed by rubbing

How does static charge build up?

It can build up when two insulating materials are rubbed together, such as a plastic comb moving through hair

What causes electrons to be transferred from one material to another?

Friction

When you rub two insulators together, what happens to the charges of the two insulators?

One material ends up with more electrons, so it has an overall negative charge

One material ends up with fewer electrons, so it has an overall positive charge

What are electrical insulators?

Materials that do not allow charges to move easily

What happens if you rub a neutral plastic rod with a paper towel?

The end of the plastic rod that was rubbed would become charged and the other end would remain neutral, meaning the plastic rod is an electrical insulator (the charges on one end did not transfer to the other end

What are examples of electrical insulators?

• Glass

• Dry wood

• Ceramics

• Plastics

• Rubber

What are electrical conductors?

Materials that allow electrons to move freely

Why are metals good conductors?

Metal atoms have at least one valence e- that can be easily transferred

Free electrons are the electron(s) in metals that are free to move throughout the conductor

Which of the two: insulators or conductors, can retain static charge?

Insulators can retain static charge

Conductors cannot retain static charge

What is the unit of electric charge?

Coulomb (C)

How many electrons need to be transferred to produce one coulomb?

It takes the addition/removal of 6.25 x 10 to the 18 electrons to produce 1C of charge

How do you measure static charge?

With an electroscope

How does an electroscope work?

• An object with a suspected static electric charge is brought near the metal knob

• Electrical charged move to the metal and down to the foils

• Since each foil (a thin metal leaf) has the same charge (positive or negative), they repel each other and separate

What is a Van de Graaff generator?

It is a machine that uses friction to produce a large static charge on a metal dome

What is lightning?

The result of a buildup of static charge in clouds due to friction created as hot air rises rapidly and ribs against ice crystals and dust particles in cloud banks

How do we use static electricity?

We use it for plastic wrap, to make it so the plastic wrap clings to whatever is is covering

We use it to decrease air pollution (devices in chimneys attract particles of dust and smoke)

Paint used to paint cars is given an electric charge, charged paint particles stick to the metal

What is grounding?

The process of the process of allowing charge to flow into the earths surface

A lightning rod is placed on top of a building, so if lightning comes near, the charge will pass through the rod into the ground, rather than through the building, which can be dangerous