1. How many different ways can a test charge be forced to the right in the diagram? Welcome to a Great Physics Day!

2. Today’s Agenda: Discuss yesterday’s assignment Lesson: Potential Difference and Capacitance (Sec. 21.2) HW: Pg. 586 #76-83 (for tomorrow) Study pg. 573-577 (by Friday’s test)

3. Learning Goal: Students will be able to… Explain (sort of) what is meant by electric potential difference. Solve problems with the formulas  V=W/q and  V=Ed. Describe what capacitors are used for, and how they work. Perform calculations with the equation C=Q/V.

4. Potential Difference:  V = W/q Potential Diff. Small Test Charge moving in the Field Work done in moving q Units: J/C = Volts (V)

5. Potential Difference:  V = Ed Potential Diff. between 2 parallel plates Distance between the plates E-field between the plates

6. Example: The electric field intensity between two charged plates is 3,200N/C. If the plates are separated by 1.5cm, what is the potential difference between the plates? How much work is required to move an electron from one plate to the other?

7. Capacitance: A capacitor is a device designed to store charge. A basic capacitor consists of two parallel plates separated by some distance, which can be charged by connecting the two plates across a potential difference.

8. Capacitance: Batt ++++++++ --------

9. Capacitance: For a given size and shape of capacitor, the charge stored depends on the potential difference (of the battery).

10. Capacitance: Another way to say this: The ratio of charge to potential difference is a constant (for a given capacitor). C = Q / V Charge Stored Units: C/V = Farads (F) Potential Diff. Capacitance

11. Example: A certain capacitor is connected to a 6.0V battery, and 9.6x10 -12 C of charge is stored. What is the capacitance of this capacitor?

12. HW Answers: 76.50V 77.1.4J 78.7.2x10 -17 J 79.100C 80.90V 81.3500N/C 82.2.00  F 83.150V Pg. 586 #76-83