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Devil physics The baddest class on campus IB Physics

Devil physics The baddest class on campus IB Physics. Potential Field Experiment. Tsokos Lesson 5-1 Electric Charge. Introductory Video Electrical Charge and Potential. IB Assessment Statements. Electric Potential Difference 5.1.1. Define electric potential difference .

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Devil physics The baddest class on campus IB Physics

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  1. Devil physicsThe baddest class on campusIB Physics

  2. Potential Field Experiment

  3. Tsokos Lesson 5-1Electric Charge

  4. Introductory VideoElectrical Charge and Potential

  5. IB Assessment Statements • Electric Potential Difference • 5.1.1. Define electric potential difference. • 5.1.2. Determine the change in potential energy when a charge moves between two points at different potentials. • 5.1.3. Define the electronvolt. • 5.1.4. Solve problems involving electric potential difference.

  6. IB Assessment Statements • Electric Current and Resistance • 5.1.5. Define electric current. • 5.1.6. Define resistance. • 5.1.7. Apply the equation for resistance in the form where ρ is the resistivity of the material of the resistor. • 5.1.8. State Ohm’s Law.

  7. IB Assessment Statements • Electric Current and Resistance • 5.1.9. Compare ohmic and non-ohmic behavior. • 5.1.10. Derive and apply expressions for electrical power dissipation in resistors. • 5.1.11. Solve problems involving potential difference, current and resistance.

  8. Objectives • Appreciate that there is a force between electric charges and that vector methods must be used to find the net force on a given charge • Describe the methods of charging by friction and electrostatic induction, and outline their differences

  9. Objectives • Understand the use of the electroscope • Understand that charge resides on the outside surface of a conductor – the net charge inside a conductor is zero

  10. Objectives • Use the formula for the electric force between point charges (Coulomb’s law)

  11. Electric Charge • Electricity is the study of electric charge • Two kinds of charges: positive and negative • Positive charge resides on protons • Negative charge resides on electrons

  12. Electric Charge • Electrons • Electrons are lighter, move easier and reside on the outer shell of the atom • Thus the flow of electricity in solid bodies is due to the motion of electrons • In liquids and gases, positive ions can also transport charge • Electrons carry the smallest unit of charge of any free particle

  13. Electric Charge • It is quantized – the charge on a body is always an integral multiple of the charge on one electron • The charge on one electron is 1.6x10-19C • The energy carried by 1 electron volt (eV) or 1.6x10-19 J

  14. Electric Charge • All materials are classified as either conductors or insulators (unless it is a semi-conductor) • Conductors have many free electrons so electricity flows freely through them • Insulators, well, don’t • Semiconductors have properties of both • Tend to have greater conductive properties under certain circumstances

  15. Electric Charge • Electric charge is conserved like total energy – cannot be created or destroyed • Electrons are not destroyed • Charge is merely balanced • The total charge of an isolated system cannot change

  16. Electric Charge • If two identical conductors have charges of 7µC and -12µC respectively. If the two are allowed to touch and then separated, what will be the charge on each?

  17. Electric Charge • If two identical conductors have charges of 7µC and -12µC respectively. If the two are allowed to touch and then separated, what will be the charge on each? • When the two spheres touch, the net charge will be -5µC. When they separate, each conductor will take half the charge, so each one will have a charge of -2.5µC.

  18. Electric Force • Observation shows that there is a force between electric charges • Like charges repel each other • Opposite charges attract each other • Magnitude of the force is directly proportional to the size of the charge, AND inversely proportional to the square of the distance between them

  19. Charging by Friction • If two different materials are rubbed together, one will pass electrons to the other • Based on respective triboelectric properties • One material is more apt to give up electrons, the other is more apt to capture electrons • When materials come in contact, they ‘adhere’ to each other chemically and electrons are passed • When they are separated, each has a net charge • Referred to as static electricity which is really just stored charge

  20. Charging by Induction

  21. Charging by Induction

  22. Charging by Induction

  23. Charging by InductionElectroscope

  24. Charging by InductionElectroscope

  25. Charging by InductionElectroscope • Why did the electrons move to ground?

  26. Charging by InductionElectroscope • Why did the electrons move to ground? • Electrons will always move to higher potential • When the negatively charged rod was brought near, positive moved to the ball while negative charge moved to the leaves giving them a negative charge • Ground, by definition, has a charge of zero • When grounded, charge will flow from negative potential to the higher zero potential

  27. Electrostatic Experiments • In static electricity, i.e. a material is holding a charge, the charge on the conductor resides on the outside of the conductor • The net charge in the center remains zero

  28. Electrostatic Experiments

  29. Electrostatic Experiments

  30. Coulomb’s Law • Magnitude of the force between charges is directly proportional to the size of the charge, AND inversely proportional to the square of the distance between them

  31. Coulomb’s Law • ε0 is the electric permittivity of a vacuum • ε0 = 8.85x10-12 C2 N-1 m-2 • k = 8.99x109 N m2 C-2 • Notice the similarity to Newton’s Law of Universal Gravitation?

  32. Coulomb’s Law • Sample Problem

  33. Summary Review • Can you appreciate that there is a force between electric charges and that vector methods must be used to find the net force on a given charge? • Can you describe the methods of charging by friction and electrostatic induction, and outline their differences?

  34. Summary Review • Do you understand the use of the electroscope? • Do you understand that charge resides on the outside surface of a conductor – the net charge inside a conductor is zero?

  35. Summary Review • Can you use the formula for the electric force between point charges (Coulomb’s law)

  36. IB Assessment Statements • Electric Potential Difference • 5.1.1. Define electric potential difference. • 5.1.2. Determine the change in potential energy when a charge moves between two points at different potentials. • 5.1.3. Define the electronvolt. • 5.1.4. Solve problems involving electric potential difference.

  37. IB Assessment Statements • Electric Current and Resistance • 5.1.5. Define electric current. • 5.1.6. Define resistance. • 5.1.7. Apply the equation for resistance in the form where ρ is the resistivity of the material of the resistor. • 5.1.8. State Ohm’s Law.

  38. IB Assessment Statements • Electric Current and Resistance • 5.1.9. Compare ohmic and non-ohmic behavior. • 5.1.10. Derive and apply expressions for electrical power dissipation in resistors. • 5.1.11. Solve problems involving potential difference, current and resistance.

  39. Questions?

  40. Homework • Lsn 5-1, #1-15

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