1. A uniform electric field, with a magnitude of 600 N/C, is directed parallel to the positive x-axis. If the potential at x = 3.0 m is V, what is the potential at x = 1.0 m?
b V
c V
d V
a. 400 V
PHY 2049: Physics II
Coulomb’s law, electric field, Gauss’ theorem and electric potential.
-W = qΔV
Energy conservation applies. U F V E

2. PHY 2049: Class Quiz
If 500 J of work are required to carry a charged particle between two points with a potential
difference of 20V, the magnitude of the charge on the particle is:
A C
B. 12.5C
C. 20C
D. cannot be computed unless the path is given
E. none of these
E=25C

3. PHY 2049: Physics II
What is the potential at the center point (in units of kq/d) ?
a) -7 (b) -5 (c) -7 (d) -7

4. PHY 2049: Physics II Calculate the Electric Field at P
Calculate the el. potential at P

5. PHY 2049: Physics II Point charge Distribution of charges
Line charge at an edge
Disc on an axis through the center

6. Some old business:
What is the electric field
of a shell
of a uniform spherical charge distribution?
What is the potential for each of the above?

7. PHY 2049: Physics II Some old business
The potential of a uniform spherical charge.
Calculate electric field, integrate it to get the potential E r R V V

8. Two particles with charges Q and -Q are fixed at the vertices of an equilateral triangle with sides of length a. The work required to move a particle with charge q from the other vertex to the center of the line joining the fixed particles is:
A. 0
B. kQq/a
C. kQq/a2
D. 2kQq/a
E. 1.4kQq/a a

9. PHY 2049: Physics II a= 39 cm q1 = 3.4pC q2 = 6 pC E at the center?
What is the potential at the center?
Keep in mind that electric field is a derivative and one needs V(x,y,z) and not just V(0,0,0) at the center.

10. PHY 2049: Physics II An outline
Capacitors, plate, coaxial, spherical..
Energy, Dielectric strength, Dielectric constant.
Netweorks: Parallel and Series configuration.

11. PHY 2049: Physics II Capacitors: A device to hold charge.
It is held by Coulomb force between the charges. +q and –q on two separate places.
V : potential difference: q= CV
C: capacitance units farad.

12. PHY 2049: Physics II

13. PHY 2049: Physics II

14. Potential near a sheet charge

15. Potential near a sheet charge

16. PHY 2049: Physics II

17. PHY 2049: Physics II
What about the

18. PHY 2049: Physics II

19. HITT
A uniform electric field, with a magnitude of 600 N/C, is directed parallel to the positive x-axis. If the potential at x = 3.0 m is 1000 V, what is the potential at x = 1.0 m?
a. 400 V b V c V
d V c

20. PHY 2049: Physics II
What is the capacitance of various familiar balls.
C = 4πεoR = R(m) F
Basketball-it is an insulator
Van de Graff top
Earth (radius 6.4 X 106 m)
CE = 0.71 mF

21. PHY 2049: Physics II Energy stored in a capacitor
U = ½ CV2 = Q2/2C = ½ QV
Dielectric Strength (oops I burned it/broke it)
Capacitor Enhancement by inserting a dielectric:
Replace εo by κεo

22. PHY 2049: Physics II

23. PHY 2049: Physics II
Ceq = C1+C2+C3

24. PHY 2049: Physics II

25. PHY 2049: Physics II Charging and discharging of capacitors.

26. PHY 2049: Physics II
25.20

27. PHY 2049: Physics II
Switch closed on left, capacitor C1 is being charged
We have C2 = C3 = 20 μF in parallel. The equivalent capacitor is then Ceq = 40 μF. When the switch is thrown to right, the battery is disconnected, the charge is shared between the capacitors C1 and Ceq = 40. What is the charge on old C2 and C3? Is your answer 40 μC? What is your answer if C2 = 10 μF and C3 = 30 μF?

28. PHY 2049: Physics II All about capacitors Capacitance units Farad
C = 4 π κεo R for a sphere of radius R and dielectric constant κ.
Energy stored dielectrics and strength
Parallel and series elements in a network