1. Aim: How do we explain the transfer of electric charge?

2. Do Now: List two quantities that we studied in class which are conserved in a closed system. Momentum and Energy

3. Conservation of Charge
The total charge of a system does not change over time. Charge is conserved. Charge cannot be created or destroyed only transferred.

4. How do we charge objects?
Charging by Friction (Rubbing)
Charging by Conduction
Charging by Induction

5. Charging by Friction
When certain objects are rubbed together, they acquire electric charge.
Examples:
Rubber and Fur- Electrons will move from the fur to the rubber rod. The fur becomes positively charged and the rubber rod becomes negatively charged.
Glass and silk- Electrons will move from the glass to the silk. The silk becomes negatively charged and the glass rod becomes positively charged.

6. Rubbing by Friction Questions
A glass rod becomes positively charged when rubbed with silk. This is because
Electrons are transferred from the silk to the glass rod.
Protons are transferred from the silk to the glass rod.
Electrons are transferred from the glass rod to the silk.
Protons are transferred from the glass rod to the silk.

7. Charging by Friction

8. Conductors and Insulators
Conductors are materials through which charges can move easily.
Insulators are materials through which charges cannot move easily.
Practice: List three conductors and three insulators that you encounter in life.
Conductors: Copper, Graphite, Tungsten (Metals)
Insulators: Plastic, Glass, Wood

9. Charging through Conduction
Assuming that we have two equally sized conducting spheres, charge will flow between the two spheres until the charges on both spheres are equal. Electrons will flow from high concentration to lower concentration. What happens to the total charge of a system over time? It stays the same

10. Conduction Examples
Conductor A has a charge of -10 C and Conductor B has a charge of – 2 C. The conductors are allowed to touch and then separated. What will be the charge on each conductor afterwards? -6 C
Conductor A has a charge of + 6 C and conductor B is neutral. The conductors are allowed to touch and then separated.
+3C

11. Conduction Examples
3. Conductor A has a charge of + 4 C. Conductor B has a charge of -8 C. Conductor C has a charge of – 2 C. Conductors A and B are allowed to touch and separated. Conductors B and C are allowed to touch and separated. What is the charge on conductors A, B, and C? Charge on A = -2C, Charge on B=-2C, Charge on C=-2C

12. Grounding
Grounding is the process of removing the excess charge on an object by means of the transfer of electrons between it and another object of substantial size. When a charged object is grounded, the excess charge is balanced by the transfer of electrons between the charged object and a ground.

13. Charging by Induction
Charging by induction requires no contact. When an object is charged by induction, the object’s overall charge does not change. However, the distribution of charges on the object does charge.

14. Induction Question
Why does a negatively charged balloon stick to a wall?
Draw a picture

15. Induction Question
2. Sphere S hangs from the ceiling. Sphere T is negatively charged. When sphere T is brought near sphere S, it attracts it. Design two experiments that we can use to determine the charge on sphere S. Experiment 1: Bring a positively charged object near S. If S attracts it, S is neutral. If S repels it, S is positive. Experiment 2: Bring a neutral object near S. If nothing happens, S is neutral. If S attracts it, S is positive. S T

16. Reviewing concepts of conduction and induction

17. Electroscopes
Electroscopes are devices which detect whether a given object is electrically charged. (It does not determine what the electric charge is).

18. Question
Which diagram shows the leaves of an electroscope charged negatively by induction? 2

19. Charging an electroscope by conduction
What about charging an electroscope by conduction with a positively charged metal sphere?

20. Charging an electroscope by induction

21. Grounding a Positively charged electroscope

22. Grounding a Negatively Charged Electroscope