ELECTRIC CHARGE. Just as the mass of the earth exerts an invisible force on you because of your mass. Any two objects which have an electric charge also exert a force on each other. The electricity on the comb is not moving so it is called:. STATIC ELECTRICITY.
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little comb BIG EARTH Gravity Which is stronger Electrical Force paper
If I had a bunch of electrons (1024) in two piles, separated by a millimeter 1 mm Their masses would attract each other due to gravity with a force of: .00000000000000000000000000000000000000006 N Their Charges would repel each other with an Electrical force of: 230 N
The reason that Electrical Forces aren’t very noticeable compared to gravity even though it is MUCH stronger is that: Objects are electrically neutral for the most part. So the attractive forces pretty much cancel out the repulsive forces
+ - Our charge cannot not be split into a smaller piece of charge
Conservation of Charge Charge is not created or destroyed, but it can move from 1 object to another
Some materials are very good at holding onto their own electrons or stealing them from other objects. Like: Plastics and Rubber Others don’t hold on to their electrons well and can’t steal them from other objects. Like: hair or glass
+ - + - + - When two materials are rubbed, usually electrons get stolen by one the of the objects. They start out with NO NET CHARGE. Why are they neutral? + + cloth + - - - glass
+ + + - After the electrons move. What it the charge on each object? Negative - + + cloth + - - - - Positive glass
+ - + - + - If a piece of Plastic is rubbed on the same cloth (neutral again) + + cloth + - - - rubber
+ - + - + - If a piece of Plastic is rubbed on the same cloth (neutral again) + + cloth + - - - rubber
- - + - + - + - They both end up charged + + Positive cloth + - Negative rubber
CHARGE IS NOT CREATED It is only transferred between OBJECTS 2+ 0 + + + + - - + - + - 0 2- e-s + 2e-s - + - + - + - - + + - - - 2+ + 2- = 0 0 + 0 = 0
RECAP How does an object become negatively charged It GAINS Electrons positively charged It LOSES Electrons An object DOES NOT gain protons to become positively charged. This would be a NUCLEAR REACTION.
BEN FRANKLIN FOUND THAT + + Repel + + + + + + - - - - Attract + + - + + - - - + + - - - - Repel + + - - + + - - So he knew that the charges were different - -
Force of Gravity Coulombic Force Proportional to mass Proportional to charge 6.667 10-11 (little) 8.988 109(BIG) k Q1 Q2 G m1 m2 F = F = r2 r2 BOTH FOLLOW INVERSE SQUARE LAW
Force of Gravity Coulombic Force Charge can be positive or negative Mass is always positive k Q1 Q2 G m1 m2 F = F = r2 r2 Always attractive Can be attractive or repulsive
What force is felt by the electron in a hydrogen atom from its nucleus. The radius of a hydrogen atom is 5.3 x 10-11 m How would the force change if the radius was doubled? How would the force change if the nucleus had two protons? What if the charge on both were doubled?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - If a charge is placed on a conductor, the like charges repel each other and migrate to the surface to get as far as possible from other like charges. - - - + + - + - + - - + + Negatively charged metal sphere Positively charged metal sphere
If a charge is placed on a INSULATOR, electrons are stuck where they land. So charged patches can be seen. - - - - - - - - - - - - - like your black slate desk top - - - - - - - What would have happened to cause a positive patch your desk?