Basics of Static Electricity

Static electricity is when electrical charges build up on the

surface of a material and stays there (static). It is usually

caused by rubbing two neutral materials together. The

resulting build-up of static electricity is that objects may be

attracted to each other or, even cause a spark to jump

from one to the other. Common examples of static

electricity in action are static cling, fly-away hair and the

sparks that can occur when you touch something.

Questions you may have include:

What causes static electricity?

Why do things attract or repel?

What causes a spark?

This lesson will answer those questions and explain the

concepts concerning finding static electricity.

Cause of static electricity

Static electricity is usually caused when certain materials

are rubbed against each other, like wool on plastic or the

soles of your shoes on the carpet. The process causes

electrons to be pulled from the surface of one material

and relocated on the surface of the other material.

Rubbing a balloon on a wool sweater

creates charges on the surfaces

The material that loses electrons ends up with an excess of

positive (+) charges. The material that gains electrons ends

up an excess of negative (-) charges on its surface.

Electrons pulled from orbit

The gain or loss of electrons can be explained by recalling

that atoms consist of a nucleus of neutrons and positively-

charged protons, surrounded by negatively-charged

electrons. Normally, there are the same numbers of

electrons as protons in each atom.

However, if Object A pulls electrons from their orbit or

shell around the nucleus of Object B, it will cause Object A

to have a negative charge because it has more electons

than protons. Likewise, Object B will have extra protons in

its shell, giving it a positive charge.

Prefers dry air

When the air is humid, water molecules can collect on the

surface of various materials. This can prevent the build-up

of electrical charges. The reason has to do with the shape

of the water molecule and its own electrical forces.

Thus, static electricity is formed much better when the air

is dry or the humidity is low.

Force field causes attraction

An object that has static electricity charges built up on its

surface has an electrical force field coming from the

surface. This field will mildly attract neutral objects or

those with no charge. The field will strongly attract an

object that has an opposite charge on its surface. From

this we get the expression: "Opposites attract."

If two objects have the same charge, the electrical force

field will cause those objects to push away from each

other or repel.

Law of Electrical Charges

Like charges repel each other and unlike charges attract

each other. Magnets, fly –away hair.

Charged articles will attract opposite charged and neutral

objects, but will only repel like charged objects.

Attraction

Rub a balloon on a wool sweater. The balloon collects

negative electrical charges on its surface and the wool

collects positive charges. You can then stick the balloon to

the wall, which does not have an excess of either charge.

The balloon will also stick to the wool, although the

charges may jump back to the original material in a short

time.

You can also run a comb through your hair to charge the

comb with static electricity. The comb can then be used to

attract neutral pieces of tissue.

Picking up tissue with a comb

Repulsion

Comb your hair on a dry day or after using a hair drier. The

plastic comb collects negative charges from the hair,

causing the hair to have an excess of positive charges.

Since like charges repel, the hair strand will tend to push

away from each other, causing the "fly-away hair" effect.

Why sparks fly

When two objects that have opposite charges get near

each other, the electrical field pulls them together.

What actually happens is that the negatively-charged (-)

electrons are attracted to the atoms in the other material

that have an excess positive (+) charge. Things are much

more stable if all the atoms have an equal number of (+)

and (-) charges.

Strong forces hold electrons

The reason the electrons can't leave their present material

is because of strong molecular forces that keep them

where they are. If there are enough positive (+) charges

attracting them, and the distance is not too great, some of

the electrons will break loose and fly across the gap to the

(+) side.

Once it starts

Once a few electrons start, it heats up the air. (Think about

the heat that is created when you rub your hands

together.) Then more and more jump across the gap,

heating the air even more. This happens very fast, and the

air gets so hot that it glows for a short time. This is a spark.

The same thing happens with lightning, except on a much

larger scale, with higher voltages and current.

Ben Franklin

Ben Franklin proved that lightning was static electricity by

flying a kite in a storm and detecting static electricity by

seeing the hairs on the kite string stand on end and

creating a spark with a metal key. This dangerous

experiment showed that static electricity was being

formed in the clouds by the rain.

In conclusion

Rubbing certain materials together can cause the build-up

of electrical charges on the surfaces. Opposite charges

attract and same charges repel. Either charge will be

attracted to something of neutral charge. Sparks are an

extreme case of electrons being attracted to an object that

is positively-charged.