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Chapter 20 Static Electricity

Chapter 20 Static Electricity. Electrostatics - The study of electrical charges that can be collected and held in one place. Chapter 20 Static Electricity. Chapter 20 Static Electricity.

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Chapter 20 Static Electricity

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  1. Chapter 20 Static Electricity • Electrostatics - The study of electrical charges that can be collected and held in one place.

  2. Chapter 20Static Electricity

  3. Chapter 20Static Electricity • Every atom is composed of a positively charged nucleus, around which are distributed a number of negatively charged electrons. • Electrons of all atoms are the same. Each has the same quantity of negative charge and the same mass. • Protons and neutrons compose the nucleus. Protons are 2000 times more massive than an electron and carry an equal amount of charge. • All normal atoms have equal number of protons and electrons.

  4. Chapter 20Static Electricity

  5. Chapter 20Static Electricity

  6. Chapter 20Static Electricity • Charged versus Uncharged Objects • Positively-Charged Possesses more protons than electrons • Negatively-Charged Possesses more electrons than protons • Uncharged Equal numbers of protons and electrons

  7. Chapter 20Static Electricity • Electric Charge: • Positive or negative • Charge is quantified • Like charges repel, opposites attract • Charges exert a force through a distance. • The force is stronger when the charges • are close together

  8. Chapter 20Static Electricity

  9. Chapter 20Static Electricity

  10. Chapter 20Static Electricity

  11. Chapter 20Static Electricity • Grounding Connecting a charged object to earth to remove an object’s charge. • Conductor Any material through which an electric charge is readily transferred. • Insulator Any material through which an electric charge is not readily transferred. • Induction The process of charging an object by bringing it into the electric field of another object.

  12. Chapter 20Static Electricity

  13. Chapter 20Static Electricity

  14. - + Chapter 20Static Electricity Charge by Conduction

  15. + + + - + + + + + + + Chapter 20Static Electricity Charge by Induction

  16. Chapter 20Static Electricity

  17. Chapter 20Static Electricity

  18. Chapter 20Static Electricity

  19. Chapter 20Static Electricity Coulomb The quantity of electric charge 1 coulomb = 6.25 x 1018 electrons 1 electron = 1.6 x 10-19 coulombs

  20. Chapter 20Static Electricity Coulomb’s Law The force between two charged objects vary directly with the product of their charges and inversely as the square of the distances between them. F force (N) q charge (C) k 9 x 109 N •m2/ C2 Inverse Square Law

  21. Chapter 20Static Electricity Find the force of attraction between charges of 100 µC and -50 µC separated by a distance of 50 cm. q1 = 1 x 10-4 C q2 = -5 x 10-5 C D = .5 m k = 9 x 109 N •m2/ C2

  22. Chapter 20Static Electricity Find the force of attraction between charges of 100 µC and -50 µC separated by a distance of 50 cm. F = -180 N The negative means a force of attraction

  23. Chapter 20Static Electricity Two charges are separated by 4.0 cm. Object A has a charge of +5 µC and object B has a charge of +3 µC. What is the force on object A? q1 = 5 x 10-6 C q2 = 3 x 10-6 C D = .04 m k = 9 x 109 N •m2/ C2

  24. Chapter 20 Static Electricity Two charges are separated by 4.0 cm. Object A has a charge of +5 µC and object B has a charge of +3 µC. What is the force on object A? F = 84 N The positive means a force of repulsion

  25. Chapter 20Static Electricity A positive charge of 3.5 x 10-6 C has 2 charges nearby. One has a negative charge of -1.2 x 10-6 C and is .03 m away at 180°. The second charge is a positive charge of 3 x 10-6 C at 270° at .02 m. What is the total force on the 3.5 x 10-6 C charge?

  26. F2 .03 m + + - F1 .02 m + Chapter 20Static Electricity

  27. F2 + F1 Chapter 20Static Electricity F1 = 42 N F2 = 236 N

  28. F F2 = 236 N + F1 = 42 N Chapter 20Static Electricity F2 = (42 N)2+ (236 N)2 = 57460 F = 240 N tan = 42 N/236 N = .178  = 10° The force on the 3.5 x 10-6C is 240 N at 100º

  29. Chapter 20Static Electricity A negative charge of 4.5 µ C has 2 charges nearby. One has a negative charge of 1.2 µC and is .04 m away at 90°. The second charge is a negative charge of 2.1µC at 180° at .03 m. What is the total force on the 4.5 µC charge?

  30. - .04 m .03 m F1 - - - F2 Chapter 20Static Electricity

  31. F1 - F2 Chapter 20Static Electricity F1 = 95 N F2 = 30 N

  32. Chapter 20Static Electricity 95 N F2 = (30 N)2+ (95 N)2 = 9736 - φ F = 99 N 30 N tan  = 30 N/ 95 N = .315  = 17° The force on the 4.5 µC is 99 N at 343º

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