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ELECTRIC CHARGE

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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ELECTRIC CHARGE

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  1. ELECTRIC CHARGE

  2. 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.

  3. The electricity on the comb is not moving so it is called: STATIC ELECTRICITY the study of stationary charges is called: ELECTROSTATICS

  4. little comb BIG EARTH Gravity Which is stronger Electrical Force paper

  5. 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

  6. In Mechanics, the primary factor was MASS. We never really said what it is, just how it behaves. Gravity Inertia Momentum Energy

  7. With Electrostatics, the primary factor is CHARGE We won’t define what it is or why it acts as it does, just how it behaves.

  8. There are ONLY 2 types of charges Positive (+) Negative (-)

  9. LIKE CHARGES REPEL + + - -

  10. OPPOSITE CHARGES ATTRACT - +

  11. - + + - All charge in the universe comes from two of the particles that make up an atom Electrons (-) Protons(+) Neutrons (no charge)

  12. Electrons (-) Protons(+) - + + - Do the charge particles attract or repel each other in an atom? BOTH

  13. - + + - The neutrons job is to hold the nucleus together Neutrons (no charge)

  14. + - The electron is the smallest piece of negative charge The proton is the smallest piece of positive charge - Their charges are EQUAL but OPPOSITE +

  15. If an object has the same number of protons as electrons, It has no NET CHARGE (Electrically Neutral) + - - +

  16. 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

  17. - NEUTRAL + + - - Positive Net Charge (+1) + + - Negative Net Charge (-1) + + - -

  18. + - Our charge cannot not be split into a smaller piece of charge

  19. Conservation of Charge Charge is not created or destroyed, but it can move from 1 object to another

  20. 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

  21. + - + - + - 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

  22. + + + - After the electrons move. What it the charge on each object? Negative - + + cloth + - - - - Positive glass

  23. + - + - + - If a piece of Plastic is rubbed on the same cloth (neutral again) + + cloth + - - - rubber

  24. + - + - + - If a piece of Plastic is rubbed on the same cloth (neutral again) + + cloth + - - - rubber

  25. - - + - + - + - They both end up charged + + Positive cloth + - Negative rubber

  26. CHARGE IS NOT CREATED It is only transferred between OBJECTS 2+ 0 + + + + - - + - + - 0 2- e-s + 2e-s - + - + - + - - + + - - - 2+ + 2- = 0 0 + 0 = 0

  27. thus CHARGE IS CONSERVED 0 + 0 = 0 (2+) + (2-) = 0 0 = 0 Initial = Final

  28. 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.

  29. BEN FRANKLIN FOUND THAT + + Repel + + + + + + - - - - Attract + + - + + - - - + + - - - - Repel + + - - + + - - So he knew that the charges were different - -

  30. I dub the charge on the glass rod POSITIVE. And Rubber rod shall be NEGATIVE + + + - + - - This was arbitrary + - + - -

  31. The smallest Net charge an object can have is that of 1 electron - + 1- - + 1+

  32. The SI unit of CHARGE is a COULOMB (C) The smallest possible charge an object can have is e = 1.60 x 10-19 C All charge is in multiples of this

  33. How many electrons do I need to have 1 full coulomb of charge? e = 1.60 x 10-19 C

  34. The force exerted between two charged objects is Charge on object #1 (C) Charge on object #2 (C) k Q1 Q2 F = r2 distance between (m) r Q1 Q2

  35. Which charge feels the greater force? SAME!!! k Q1 Q2 F = r2 r F12 = F21 (N) +1 +2

  36. Fudge Factor = 8.988 109 N m2 C2 k Q1 Q2 F = r2 This equation is known as COULOMB’S LAW

  37. What force is felt between, two objects each with 1 Coulomb of NET Charge separated by 1 m? k = 8.988 109 N m2 C2 k Q1 Q2 F = r2

  38. 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

  39. 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

  40. 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?

  41. Electrons can travel easily through some materials but not other materials

  42. It is easier for electrons to travel hundreds of miles through metal wire than it is a few centimeters of rubber

  43. Conductor- electrons are free to move around. Insulator- electrons are held in place strongly

  44. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 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

  45. 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?

  46. Friction (rubbing) is not the only an object can be charged

  47. Starting with a negatively charged sphere and a neutral one separated by air Negative Metal Sphere Neutral Metal Sphere - - - - - - Note: the extra electron on this sphere repel each other and spread out

  48. They electrons (repelling) are able to spread out further, charging the other sphere! If they are brought into contact - - - - - - The second sphere was charged by CONDUCTION. CONDUCTION- Charging by contact.

  49. COPPER - - - - - - COPPER - - - - - - The charge was CONDUCTED, through the copper

  50. Glass - - - - - - Glass - - - - - - NO CONDUCTION THROUGH AN INSULATOR

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