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Concept Summary Adapted from: Batesville High School Physics

Electrostatics. Concept Summary Adapted from: Batesville High School Physics. Electrostatics. Electrostatics is the study of electric charge at rest . (Or more or less at rest, as opposed to current electricity.). Electrical Charges.

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Concept Summary Adapted from: Batesville High School Physics

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  1. Electrostatics Concept Summary Adapted from: Batesville High School Physics

  2. Electrostatics • Electrostatics is the study of electric charge at rest. • (Or more or less at rest, as opposed to current electricity.)

  3. Electrical Charges • Electric charge is a fundamental property of matter. • Two types of electric charges • Positive charge - every proton has a single positive charge. • Negative charge - every electron has a single negative charge.

  4. Electrical Forces • Like charges repel. • Opposite charges attract.

  5. Likes Repel, Opposites Attract

  6. Elementary Charges • Protons carry the smallest positive charge. • The smallest negative charge is the charge on the electron. • The charges carried by the proton and electron are equal in size. • The mass of the proton is about 2000 times the mass of the electron.

  7. Units of Charge • The SI unit of charge is the coulomb. • The elementary charge of a proton or an electron is 1.60 x 10−19 C. • The proton is positively charged, while the electron is negatively charged.

  8. Electrical Charge • An object with an excess of electrons is negatively charged. • An object with too few electrons (too many protons) is positively charged. • An object with the same number of electrons and protons is neutral.

  9. Stroking If something gets a positive electric charge, then it follows that something else: a) becomes equally positively charged. b) becomes equally negatively charged. c) becomes negatively charges, but not necessarily equally negatively charged. d) becomes magnetized.

  10. Stroking If something gets a positive electric charge, then it follows that something else: a) becomes equally positively charged. b) becomes equally negatively charged. c) becomes negatively charges, but not necessarily equally negatively charged. d) becomes magnetized.

  11. Stroking If something gets a positive electric charge, then it follows that something else: a) becomes equally positively charged. b) becomes equally negatively charged. c) becomes negatively charges, but not necessarily equally negatively charged. d) becomes magnetized.

  12. Charge is Conserved • Electric charge is conserved - • Electric charge moves from one place to another - no case of the net creation or destruction of electric charge has ever been observed. • In solids, only electrons can move. • In liquids, gasses, and plasmas, both positive and negative ions are free to move.

  13. Conductors & Insulators • Materials in which charges are free to move about are called conductors. • Materials in which charges are not free to move about are called insulators.

  14. “Creating” an Electric Charge • When you “create” an electric charge (by rubbing your feet on a carpet) you are actually separating existing charges – not creating charges. • One object ends up with an excess of electrons (− charge), and the other a deficit of electrons (+ charge).

  15. Charging by Friction • If one neutral material has more affinity for electrons than another (neutral) material, it will attract electrons from the other. • One material becomes negatively charged, the other positively charged.

  16. Charging by Contact • If a charged object is brought in contact with a neutral object, charges will be repelled from (or attracted to) the charged object. • The neutral object will gain a charge of the same sign as the charged object.

  17. Grounding • Providing a path from a charged object to the Earth is called grounding it. • Charges will be attracted from (or repelled to) the Earth by the charged object. • Since the Earth is so large, both the charged object and the Earth are neutralized.

  18. Charging by Induction • Bring a charged object near (but not touching) a neutral object. • Ground the neutral object. • Remove the ground. • Remove the charged object • The neutral object now has a charge opposite to the charged object.

  19. Induction

  20. Under the Influence Two uncharged metal balls, X and Y, stand on glass rods. A third ball, Z, carrying a positive charge, is brought near the first two. A conducting wire is then run between X and Y. The wire is then removed, and ball Z is finally removed. When this is all done it is found that: a) balls X and Y are still uncharged b) balls X and Y are both charged positively c) balls X and Y are both charged negatively d) ball X is + and ball Y is − e) ball X is − and ball Y is +

  21. Under the Influence Two uncharged metal balls, X and Y, stand on glass rods. A third ball, Z, carrying a positive charge, is brought near the first two. A conducting wire is then run between X and Y. The wire is then removed, and ball Z is finally removed. When this is all done it is found that: a) balls X and Y are still uncharged b) balls X and Y are both charged positively c) balls X and Y are both charged negatively d) ball X is + and ball Y is − e) ball X is − and ball Y is +

  22. Under the Influence Two uncharged metal balls, X and Y, stand on glass rods. A third ball, Z, carrying a positive charge, is brought near the first two. A conducting wire is then run between X and Y. The wire is then removed, and ball Z is finally removed. When this is all done it is found that: a) balls X and Y are still uncharged b) balls X and Y are both charged positively c) balls X and Y are both charged negatively d) ball X is + and ball Y is − e) ball X is − and ball Y is +

  23. Electroscopes Metal plate Insulator Metal shaft Glass window Metal plate Insulated container Metal leaf

  24. Polarization • Bringing a charged object near (but not touching) a neutral object polarizes (temporarily separates) the charge of the neutral object. • Like charges in the neutral object are repelled by the charged object. • Unlike charges in the neutral object are attracted by the neutral object. • The neutral object returns to normal when the charged object is removed.

  25. Polarization

  26. Electric Dipoles • An object that is electrically neutral overall, but permanently polarized, is called an electric dipole. • Example: H20 molecule

  27. Electrical Forces • The electrical force between 2 charges depends on: • The size of each charge • More charge means more force. • The distance between the charges • More distance means less force.

  28. Electrical Forces • The electrical force between 2 charges is: • Directly proportional to each charge. • Inversely proportional to the square of the distance between the charges.

  29. Coulomb’s Law

  30. The End

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