2. Recall Gravitational PE n The work done to lift a ball of mass 1 kg a vertical height of 1 m is 10 J n What is the work done to lift 5 bowling balls?

3. Work done for total job vs. work done per ball n The work done to lift one ball is 10 J, and the work done to lift five is 50 J. The work done per ball remains 10 J.

4. Electrical PE n Assume that it takes 10 J to lift one positive charge “up” from a negative plate to a positive plate n How much will it take to “lift” 5 charges from the negative plate to the positive plate?

5. Work done for total job vs. work done per charge n The work done to lift one charge is 10 J, and the work done to lift five is 50 J. The work done per charge remains 10 J. n The electrical PE is the total work done n The electrical potential is the work done per charge (measured in J/C or volts (V))

6. Which is more dangerous? 1 x 10 -6 C at 300,000 V 150,000 C at 12 V

7. Recall: Gravitational PE n When in a uniform field, U g =mgh n In a changing field (such as around planet),

8. Electrical Potential n When in a uniform E-field, V=W/q=Ed n In a changing field (such as that around a point charge),

9. Adding potentials n The total potential at a point near many point charges is the numerical sum of the contribution from each charge. Potential is NOT a vector.

10. Equipotential lines n Equipotential lines are like the lines on a contour or topographic map – they represent levels of constant potential

12. Equipotential lines, cont. n No work is done to move along an equipotential line or curve n Equipotential lines (curves) are always perpendicular to E-field lines

13. Relationship between E and V n The magnitude of the E-field is given by the gradient of the potential