CH15 - Polarization of Conductors

The ball-and-spring model of a solid.

Uniform mobile-electron sea (blue), positive atomic cores (red + ’s).

CH15 - Polarization of Conductors

The ball-and-spring model of a solid.

Uniform mobile-electron sea (blue), positive atomic cores (red + ’s).

CH15 - Polarization of Conductors

The ball-and-spring model of a solid.

Uniform mobile-electron sea (blue), positive atomic cores (red + ’s).

Enet, inside = 0

Clicker Quiz

1. It can only be positive2. It can only be negative3. It can either be positive or neutral 4. It can either be negative or neutral

B

A

+++

++++

Two conducting spheres A and B are shown here. The sphere la-beled B is positively charged; sphere A, suspended by a string, is attracted to B. The setup is in equilibrium.

What is the sign of the net charge on A?

Clicker QuizConsider a new situation in which A is negatively charged. The magnitude of the charge on A is less than the magnitude of the charge on B. If A swings up and touches B, is it possible that A will remain in contact with B?

1. Yes2. No3. Only if the magnitude of the charge in A is much smaller than in B.

B

A

+++

++++

|qA| < |qB |

1. E =q

4 or2

2. E =q

4 o(a + r)2

3. E =q

4 o(r + a/2)2

4. E =q

4 o(r − a/2)2

5. E =q

4 o(a/2)2

Clicker QuizA particle with charge q is a distance r from the center of a cube of metal. The charge lies along the x axis and the cube’s center is at the origin. What is the magnitude of the electric �eld at the origin due to the surface charge distribution?

y

x

z

q

a

Reading Questions 15.7-15.81. The book talks about polarization of the body when you approach a charged

surface and has an illustration showing that one side of the body is positive and the other is negative. Does the polarization truly spread this much, or is it hyperbolized for e�ect? At what point does the polarization become negligible? Is this polarization something we can actually see?

2.To discharge the negatively charged tape, is it really the positive ions from your skin goes to the tape and neutralize the tape? In our previous discussion, only electron moves. Why in this case is the positive charges move?

CH16 - �eld of Distributed ChargesE

Electric Field ofDistributed Charges

Reading Questions 15.7-15.81. The book talks about polarization of the body when you approach a charged

surface and has an illustration showing that one side of the body is positive and the other is negative. Does the polarization truly spread this much, or is it hyperbolized for e�ect? At what point does the polarization become negligible? Is this polarization something we can actually see?

2.To discharge the negatively charged tape, is it really the positive ions from your skin goes to the tape and neutralize the tape? In our previous discussion, only electron moves. Why in this case is the positive charges move?

3. I am not really sure about the integral part, what exactly happened (every step) during the integration. Also, I am curious if we didn't choose the the centre of the rod to be the origin but choose another point, like the top or the end point of the rod, will the computational part be really complex?

4. The book says that deltaQ is a small portion of total charge Q, which contributes to deltaE. In the case of deltaE, is delta still representing a small portion or is it a di�erence? I'm not sure when to use the symbol for each purpose.