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Electric force

Electric force. Do Now. Electric force Towards the attracting object Charge was transferred from the cloth to the ruler. Pieces of paper were attracted to the ruler by the electric force. Gravity acts against the electric force and tries to keep the paper on the table. Do Now.

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Electric force

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  1. Electric force

  2. Do Now • Electric force • Towards the attracting object • Charge was transferred from the cloth to the ruler. Pieces of paper were attracted to the ruler by the electric force. Gravity acts against the electric force and tries to keep the paper on the table.

  3. Do Now 4. Object demonstrates electric interaction after rubbing 5. Objects rub together (this is only one way!) 6. Same charge  repel 7. Different charge  attract

  4. Do Now 8. Material through which a charge will not easily move 9. Material that allows charges to easily move 10. Electrons can move easily 11. Air is an insulator because charges do not easily move

  5. Demo

  6. Electroscope

  7. Electroscope • Electroscope=metal knob connected by metal stem to two thin, lightweight pieces of foil called leaves Metal Knob Thin metal stem Container Lightweight foil leaves

  8. Observation 1: Initial Conditions • What are the initial conditions for the electroscope? • Where are the charges located and how many of each type are there?

  9. Observation 2: Separation of charge • As the charged rod is brought closer, what happens to the leaves? • What happens to the charges?

  10. Observation 3: Conduction • What does the charged rod do? • What is the effect on the leaves? • What happens to the electrons on the rod? • What do the leaves do after the rod moves away?

  11. Observation 4: Induction • What does the charged rod do? • What is the effect on the leaves? • What happens to the electrons on the rod? • What do the leaves do after the rod moves away?

  12. What just happened? EXPLANATIONS

  13. Observation 1: Initial Conditions • Foil leaves close together • neutral charge – same amount of + and - charges

  14. Observation 2: Separation of charge • As the charged rod is brought closer, leaves move apart Polarize – separate into opposites Polarize: + and – charges separate within the object

  15. Check for Understanding & Summary • What were the initial conditions of the electroscope? • Define polarization. • How did the electroscope become polarized? • Negatively charged rod brought close to metal ball • + charges concentrate on metal knob, - charges concentrate in the leaves

  16. Observation 3: Conduction • Conduction: transferring electrons by touching a charged object to another object

  17. Observation 3: Conduction • Charged object touches the other object • Rod touches the top of the electroscope

  18. Observation 3: Conduction • 2. Electrons transferred between the objects • Electrons flow from rod to electroscope • This is b/c they repel each other and want to be far from each other

  19. Observation 3: Conduction • 3. Remove charged object. Other object is now charged • Remove rod • Electroscope has neg. charge • Leaves move away from each other

  20. Check for Understanding & Summary • Define conduction • Explain each step of conduction

  21. Observation 4: Induction Induction – transferring electrons by holding a charged object next to another object

  22. Observation 4: Induction • Charged object polarizes other object • Rod polarizes electroscope • + charges concentrate on metal knob, - charges concentrate in the leaves • Leaves spread apart • Objects do not touch • e- DO NOT leave the rod!!!

  23. Observation 4: Induction 2. Second object is grounded and electrons are transferred • Person touches electroscope • e- flow from electroscope, into person, into ground e- DO NOT leave the rod!!!

  24. Observation 4: Induction 3. Remove ground and remove charger • Person removes hand and removes rod 4. Object is now charged • Electroscope has + charge • Leaves move away from each other

  25. Check for Understanding & Summary • Define induction • Explain each step of induction

  26. Key Point • Law of Conservation of Charge – overall charge on a system is the same before and after the charging process Charges do not disappear, only transferred from one source to another

  27. Let’s expand upon what we just learned! ELABORATE

  28. van de Graaff generator

  29. Apply what you know! • Independently answer the questions in your notes

  30. Check for Understanding & Summary • 1. Upper collecting comb becomes polarized: e- move to the bottom of the brush b/c they are attracted to the + rubber belt • The upper comb is already grounded, so it becomes neg. charged by induction

  31. Check for Understanding & Summary • 2. Comb is attached to dome. Charge transferred from comb to dome by conduction • 3. Person gets close to dome and gets shocked: negative charge transferred by induction • 4. Person touches the dome – negative charge transferred by conduction

  32. BACKUP

  33. Observation 5: Induction part A

  34. Observation 6: Induction part B

  35. Observation 7: Induction Part C

  36. Observation 8: Induction Part D

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