1. Chapter 26 Electric Potential
第二十六章 電位

2. Lightning

3. Just before lightning

4. Electric potential energy

5. Electric potential energy
where W is the work done by the static electric field.
For convenience we often define
Where is the work done by the field to move the charge particle from infinity to its current position and

6. Electric potential
In general we have

7. Work done by an applied force
If ΔK = 0, then

8. Equipotential surfaces
Surfaces in space on which V is constant.

9. Equipotential surfaces
If ΔV is chosen to be the same for all adjacent equipotential surfaces, then the electric filed is inversely proportional to the separations of the equipotential surfaces.

10. Calculating the potential from the fieldor
Vi can be assigned to any convenient value such as 0.

11. Potential due to a point chargeIf

12. Potential due to a point charge

13. Potential due to an electric dipole
If the point of interest P is far away from the dipole, then

14. Potential due to an electric dipole

15. Induced dipole moment

16. Potential due to a group of point charges
Example

17. Potential due to continuous charge distribution

18. Line of charge

19. Charged disk

20. Calculating the field from the potential

21. Electric potential energy of a system of point charges

22. Potential of a charged isolated conductor

23. Surface charge density of a conductor

24. Electric fields near a conductor
The field strength is strongest at the point on a conductor where its local curvature of radius is the smallest.

25. Image charge

26. Home work Question (問題): 8, 15, 21 Exercise (練習題): 5, 12, 19
Problem (習題): 12, 28, 29, 37