1. Electric field, Electric Potential Difference and Capacitance

2. Electric Potential Difference • In an electric field, the change in potential energy per unit charge. • The work done moving a test charge in an electric field divided by the magnitude of the test charge.

3. Electric Potential Difference Equations V = electric potential difference in volts (V) W = work in Joules (J) q‘ = test charge in Coulombs (C)

4. Electric Potential Difference Equations Since W = Fd W = work in J F = force in N d = displacement in m Then, Recall that Therefore,

5. Capacitance • The ability of a material to store electric charges. • The ratio of an object’s stored charge to its potential difference • Measured in farads (F)

6. Capacitance equations C = capacitance in farad (F) q = charge in C V = potential difference in volts Note: 1 F = 1 C/V

7. Capacitor A device with a specific capacitance that is used in electrical circuits to store charge.

8. A simple capacitor

9. Capacitance Equations C = capacitance in F K = dielectric constant (no unit) A = area of the plates in m2 k = 9.0 x 109 Nm2/C2 d = distance of separation between the plates in m

10. Energy stored in capacitors