What is Electricity? What is Static Electricity? difference between them?
What is Electricity Electricity is a form of energy. Electricity is the flow of electrons. All matter is made up of atoms, and an atom has a center, called a nucleus. The nucleus contains positively charged particles called protons and uncharged particles called neutron Atom + + + Nucleus
What is Static Electricity Static electricity occurs when there is a build up of electric charge on the surface of a material. It is called static electricity because the charges don t move. The electricity we use everyday involves moving charges. Static = Charge does not move or flow
Two kinds of charges Static Electricity After being rubbed, a plastic ruler can attract paper scraps. Ruler carries electric charge. It exerts electric force on paper. This charging method is called charging by friction. The interaction between static electric charges is called electrostatics
Where do charges come from?. If electrons = protons neutral If electrons > protons gaining electrons, negative charge If electrons < protons losing electrons, positive charge
Where do charges come from? Static Electricity When a balloon rubs a piece of wool... + wool + + + + electrons are pulled from the wool to the balloon. The balloon has more electrons than usual. The balloon: charged, The wool: +charged
Where do charges come from? Static Electricity Rubbing materials does NOT create electric charges. It just transfers electrons from one material to the other.
Examples of static electricity: Static Electricity Rubbing a balloon on your hair Walking across carpet Clothes tumbling in dryer What do these have in common? Friction!!!!
Combing transfers electrons from the hair to the comb by friction, resulting in a negative charge on the comb and a positive charge on the hair.
Induced charge Charged and neutral objects (not touching) are attracted because electrons move in the neutral object. Electrons move toward a +ve charged object and away from a ve charged one. This is called induced charge
Conduction Conduction = direct transfer of charge Example : walk across carpet and touch a doorknob shocking! Electrons are stripped from the carpet and we gain a ve charge When you touch the doorknob, electrons jump onto it : electrical discharge
Rules of static electricity Static Electricity Objects with like (same) charges repel, but objects with unlike charges attract. Charged objects attract neutral objects
Does friction always create static charge? Different materials have different strength of attraction for electrons If two objects of the same material are rubbed, no static charge forms (equal number of electrons transfer each way) If two different objects are rubbed, they will have different attraction to the electrons. The stronger one will take electrons away from weaker one and static charges build up
Uses of static electricity Static Electricity Dust removal (Pollution Control) Photocopy (Xerography) Car Painting
Effect of Materials on Static Electricity Materials are listed below according how well they create static electricity when rubbed with another material, as well as what charge the material will possess. Become positive in charge Materials that gain a positive (+) electrical charge ( or tend to give up electrons) Dry human skin Leather Glass Greatest tendency to giving up electrons and becoming highly positive (+) in charge The glass on your TV screen gets charged and collects dust
Effect of Materials on Static Electricity Human hair Nylon Wool Lead Cat fur Silk Aluminium Paper "Flyaway hair" is a good example of having a moderate positive (+) charge A surprise that lead would collect as much static electricity as cat fur Gives up some electrons
Effect of Materials on Static Electricity Neutral There are very few materials that do not tend to readily attract or give up electrons when brought in contact or rubbed with other materials. Materials that are relatively neutral Cotton Steel Best for non-static clothes Not useful for static electricity
Effect of Materials on Static Electricity Become negative in charge Materials that gain a negative ( ) electrical charge Wood Nickel, Copper Gold, Platinum Polyethylene (Scotch Tape) Attracts some electrons, but is almost neutral Copper brushes used in Wimshurst electrostatic generator Attract electrons almost as much as polyester Pull Scotch Tape off surface and it will become charged
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