1. Capacitors, Batteries

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

3. Energy stored in Capacitor
E = ½ C V2 = ½ q2 /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.
CE = C1 + C2 + C3 + ……….
2μF
3μF
10μF

7. Capacitors in Series
Several capacitors in series block the flow of charge: Capacitance decreases.
1/CE = 1/C1 + 1/C2 + 1/C3 + ……….
2μF
3μF
10μF

8. Example: What is the equivalent capacitance of the entire circuit?
C1 =2μF
C2 = 4μF
C3 = 4μF
C4 = 2μF

9. What is the voltage across C1. What is the voltage across C3
What is the voltage across C1? What is the voltage across C3? What is q3 the voltage on C3?
20V
C1 =2μF
C2 = 4μF
C3 = 4μF
C4 = 2μF

10. What is the voltage across C2? What is the voltage across C4?
C1 =2μF
C2 = 4μF
C3 = 4μF
C4 = 2μF