1. Capacitors, Batteries

2. Capacitors Create a difference in Potential based upon how much charge is stored V = q/C (V) C : Capacitance C = k ε o A /d k : dielectric constant

3. Energy stored in Capacitor E = ½ C V 2 = ½ q 2 /c

4. Batteries Produce change in voltage by chemical reaction. Change in Voltage depends on type of chemical, not how much. There is no electrical energy stored in a battery, only chemical potential energy.

5. We can use a battery to “charge up” a capacitor. V C -Change in voltage around entire loop must be zero! q=C V

6. Capacitors in parallel Several capacitors in parallel behave like one larger capacitor: Capacitance increases. C E = C 1 + C 2 + C 3 + ………. 2μF2μF 3μF3μF 10μF

7. Capacitors in Series Several capacitors in series block the flow of charge: Capacitance decreases. 1/C E = 1/C 1 + 1/C 2 + 1/C 3 + ………. 2μF2μF3μF3μF10μF

8. Example: What is the equivalent capacitance of the entire circuit? 20V C 1 =2μF C 2 = 4μF C 3 = 4μF C 4 = 2μF

9. What is the voltage across C 1 ? What is the voltage across C 3 ? What is q 3 the voltage on C 3 ? 20V C 1 =2μF C 2 = 4μF C 3 = 4μF C 4 = 2μF

10. What is the voltage across C 2 ? What is the voltage across C 4 ? 20V C 1 =2μF C 2 = 4μF C 3 = 4μF C 4 = 2μF