Static Electricity

Learning Intentions

• What is static electricity?• Give some examples of static electricity.• Define conductor and insulator• What is the relationship between atomic

structure and electricity?– Draw and explain a model the theory behind

static electricity (Opposite charges repel: Like charges attract)

The story is told of Thales…

Who had a brooch made from a brownish-gold material. One day Thales noticed that the brooch was a bit dirty, so he polished it with folds of his cloak. He found that he could not get it clean. Small pieces of fluff were attracted to it and made it look worse than ever.

What do you think happen?Do you have a story like this…

Playing with…

• Rods• Fur and other material• Pieces of paper• Running water

• balloons

Experiment: Van de Graaff Generator

Predict (discuss)• Has anyone used this before?• What do you think will happen?Observe • What happens?Explain (discuss in small groups and give an explanation)• Why is this happening? Give an explanation. • How does lightning occur? What happens when you

get a shock?

Safety

Please Explain

Safety with Van de Graaff Generator

Procedure• Need a volunteer.• Stand on plastic chair and place one hand on

generator.• Turn generator on.• When finish turn generator off.• Remove hand.Examples• http://www.stmary.ws/highschool/physics/home/

notes/electricity/staticElectricity/default.htm

Previous

Think-Pair-Share

• You are in an open field where would you go if lightning strikes?– Under some dead logs– In a wooden shed with a wooden floor– Up a tree– In a tin shed with a tin floor– In your car– In the open field– Under a plastic shed.

Benjamin Franklin

• Coined the terms positive and negative charge

• Proved lighting was static electricity

• Invented lightning rod• Built a static

electricity generator

So what is actually happening….

Atom

Static Electricity

• Is the imbalance of positive and negative charges

Attraction

http://www.youtube.com/watch?v=TE2r0vjkXK0&feature=player_embedded#!

Balloon activity

Movement of Charged Particles

• If two things have different charges, they attract, or pull towards each other. If two things have the same charge, they repel, or push away from each other.

• If you charge a balloon by rubbing it on your hair, it picks up extra electrons and has a negative charge.

• Holding it near a neutral object will make the charges in that object move.

• If it is a conductor, many electrons move easily to the other side, as far from the balloon as possible.

• If it is an insulator, the electrons in the atoms and molecules can only move very slightly to one side, away from the balloon.

• In either case, there are more positive charges closer to the negative balloon. Opposites attract. The balloon sticks. (At least until the electrons on the balloon slowly leak off.)

• It works the same way for neutral and positively charged objects.

So... How does a balloon stick to a wall?

• Conductor – is a material which allows electricity to pass through it easily. E.g. Metals,

• Insulator – do not conduct electricity

So why does your hair stand on end?

So why does your hair stand on end?

• When you take off your wool hat, it rubs against your hair.

• Electrons move from your hair to the hat.

• A static charge builds up and now each of the hairs has the same positive charge.

• Remember, things with the same charge repel each other.

• So the hairs try to get as far from each other as possible. The farthest they can get is by standing up and away from the others. And that is how static electricity causes a bad hair day!

Other examples of Static Electricity• As you walk across a carpet, electrons move from the rug to

you. Now you have extra electrons and a negative static charge.

• Touch a door knob and ZAP! The door knob is a conductor. The electrons jump from you to the knob, and you feel the static shock.

• We usually only notice static electricity in the winter when the air is very dry. During the summer, the air is more humid. The water in the air helps electrons move off you more quickly, so you can not build up as big a static charge.

• Typically matter is neutrally charged, meaning it has the same number of neutrons as electrons. If it has more electrons than protons it is negatively charged. If it has more protons than electrons it is positively charged.

• Some material hold on to their electrons more tightly than others.

• The triboelectric series identifies if materials are more likely to lose or gain electrons.

Triboelectric series

Positive items (more likely to lose electrons) in the series are at the top, and negative items (more likely to gain electrons) are at the bottom:

Human hands (usually too moist, though) Very positive Rabbit Fur Glass Human hair Nylon Wool Fur Lead Silk Aluminum Paper Cotton Steel Neutral Wood Amber Hard rubber Nickel, Copper Brass, Silver Gold, Platinum Polyester Styrene (Styrofoam) Saran Wrap Polyurethane Polyethylene (like Scotch Tape) Polypropylene Vinyl (PVC) Silicon Teflon Very negative

Resources

Static Electricity- Learn about static charge and static charge by Science made Simplehttp://www.sciencemadesimple.com/static.html

Sww wiki http://10essentialscience.wikispaces.com/Static+electricity