1. Chapter 18 Electric Energy and Capacitance demonstrations

2. Electric Potential Energy  PE= -qE  d PE electric = -qEd charge electric field strength displacement from a reference point in the direction of the field Only for a uniform field Another type of Mechanical Energy

3. Figure 18-2 from p667 + d E Positive charge moves d through a uniform field +

4. Potential Energy: Electric vs Gravity earth d  PE gravity = mg  h  PE electric = -qE  d m h

5. Unit analysis PE= -qEd joules = coulombs newtons/coulomb meters E is sometimes in so and so

6. Potential Difference Potential difference is the change in electric potential measured in volts  V =  V=-E  d Units: volts=J/C Units: volts= *m

7. Potential Difference in Charges and Fields sim 2.2 V/m -4.4 V

8. Capacitors Device that stores charge Capacitance is a measure of the ability to store energy in the form of separated charges

9. Capacitance Equations Q = total charge Units: farads = C/V  0 = permittivity constant (C 2 /Nm 2) A = area of plate d = Distance between plates

10. Energy and Capacitors Equations