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Understanding Static Electricity and Electric Charge

This chapter explores the concept of static electricity, the properties of matter, and the characteristics of electric charge. It covers conductors, insulators, and semiconductors, as well as Coulomb's Law and calculations related to electric force.

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Understanding Static Electricity and Electric Charge

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  1. CHAPTER 20 Static Electricity

  2. Matter is made up of atoms. Atoms are made up of 1. Electrons 2. Protons 3. Neutrons

  3. ATOM 1. Electrons (negatively charged) 2. Protons (positively charged) 3. Neutrons (no charge)

  4. OBJECTS 1. Conductors 2. Insulators 3. Semi-Conductors

  5. OBJECTS CONDUCTORS: are objects that allow electrons to move easily through them. Example: copper, silver, earth……

  6. An object connected to the Earth, or the ground, by a good conductor, is said to be grounded. Some ground connectors are plumbing fixtures, metal faucets, sinks, and pipes.

  7. Some materials become superconductors below a certain temperature. This critical temperature is different for different materials.

  8. Example: Niobium, Tin, and Mercury, and some metallic compounds containing barium, copper, and oxygen. Uses: Filters, Powerful magnets, and Maglev high speed express trains.

  9. INSULATORS: are objects that don’t allow electrons to flow through them easily. Example: plastic, wood, rubber, and glass.

  10. SEMICONDUCTORS: are objects with electrical properties somewhere between those of insulators and conductors. Example: silicon, germanium.

  11. Uses: In complex electrical devices like the computer board.

  12. ELECTRIC CHARGE IS AN ELECTRICAL PROPERTY THAT CREATES A FORCE BETWEEN OBJECTS. 1. POSITIVE 2. NEGATIVE 3. NO CHARGE

  13. OBJECT’S CHARGE IS 1. POSITIVE- has more protons 2. NEGATIVE – has more electrons. 3.NO CHARGE – has same number of protons and electrons.

  14. ELECTRIC CHARGE Is measured in SI units of Coulombs.(C) Electron Charge = -1.6 x 10-19 C Proton Charge = 1.6 x 10-19 C

  15. ELECTRIC CHARGE 1.0 coulomb of charge means 6.25 x 1018 protons -1.0 coulomb of charge means 6.25 x 1018 electrons

  16. CHARACTERISTICS OF ELECTRIC CHARGE 1. There are two kinds of charges- positive and negative 2. Like charges repel each other and unlike charges attract one another.

  17. CHARACTERISTICS OF ELECTRIC CHARGE 3. Charges have a natural tendency to be transferred between unlike materials. 4. Electrical charges are always conserved.

  18. CHARACTERISTICS OF ELECTRIC CHARGE 5. Charges are quantized.If an object is charged, its charge is always a multiple of a fundamental unit charge 1.6 x 10-19 C. 6. The SI unit of charge is Coulomb ( C ).

  19. CHARACTERISTICS OF ELECTRIC CHARGE 7. Objects can be charged by friction, contact, and induction.

  20. COULOMBS LAW States that the electric force between two stationary charged particles has the following properties.

  21. COULOMBS LAW 1. The Force of attraction or repulsion is inversely proportional to the square of the separation r, between the two particles. 2. The Force of attraction or repulsion is proportional to the product of the magnitudes of the charges on the two particles.

  22. COULOMBS LAW 3. It is attractive if the charges are of opposite sign and repulsive if the charges have the same sign.

  23. F = k q1 q2 r2 F = Electric Force q1=charge of one particle q2=charge of other particle r = distance between charges k = Coulomb Constant

  24. F = k q1q2 r2 F = Newtons (N) q1=Coulomb (C) q2= Coulomb (C) r = meters (m) k = 9 x 109 N m2 / C2

  25. Like Charges Repel one another

  26. Unlike Charges Attract one another

  27. Problem #1 • Object A has a positive charge of 6 x 10-6 C. Object B carrying a positive charge of 3 x 10-6 C is 0.030 m away. A) Calculate the force on A. B) What would the force on A be if the charge on B were negative? A B

  28. A B

  29. Problem #2 • Two positive charges of 6 x 10-6 C are separated by 0.50 m. What force exists between the charges? A B

  30. Problem #3 • A negative charge of -6 x 10-6 C exerts an attractive force of 65 N on a second charge 0.50 m away. What is the magnitude of the second charge? A B

  31. Problem #4 • What is the total charge of 5 x 1015 electrons?

  32. Problem #5 • What is the net charge of a combination of 7 x 1012 protons and 4 x 1012 electrons.

  33. Problem #6 • A strong lightning bolt transfers about -25 C to Earth. How many electrons are transferred?

  34. Problem #7 • Two negative charges of – 3.0 x 10-6 C exert a repulsive force of 2 N on each other. By what distance are they separated?

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