Learning Intentions • What is static electricity? • What is a conductor? • What is an insulator? • Draw and explain a model the theory behind static electricity (Opposite charges repel: Like charges attract)
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
Benjamin Franklin • Coined the terms positive and negative charge • Proved lighting was static electricity • Invented lightning rod • Built a static electricity generator
How can we move electrons away from each other • Activity 1- Balloon and hair • Activity 2 - Charging a rod (paper and streaming water)
Static Electricity • Is the imbalance of positive and negative charges Attraction http://www.youtube.com/watch?v=TE2r0vjkXK0&feature=player_embedded#! Balloon activity
So... How does a balloon stick to a wall? • 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.
Conductor – is a material which allows electricity to pass through it easily. E.g. Metals, • Insulator – do not conduct electricity
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.
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 staticelectricity 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 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 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:
Resources Static Electricity- Learn about static charge and static charge by Science made Simple http://www.sciencemadesimple.com/static.html