Question

Score Name Student ID last first [25 points total] Tutorial question IV An electrically neutral cylinder is made out of a polarizable material. The cylinder is placed in a region of strong electric field that points upward A. [4 pts] Sketch bound charges on the diagram at right. Briefly explain your reasoning B. [6 pts] In what direction is the dipole moment of the cylinder? If the dipole moment is zero, state so explicitly C. [6 pts] At each of the three points marked, sketch an arrow indicating the direction of the induced electric field due to the charges of the cylinder. Points A and C are along the center axis of the cylinder, and points B and C are in the mid-plane of the cylinder. If the induced electric field at a point is zero, state so explicitly. Explain your answer X [4 pts] In what direction is the polarization density of the cylinder? Explain your reasoning. D. [5 pts] Is there a pressure on the top surface of the cylinder? Explain why or why not E.

Can someone carefully explain and answer questions A, B, C, D and E in detail, please!!!

Answer 1

A) The bound charges cannot move freely in the material, but they will be moved a tiny bit:

+ + ++ +

the positive charges will move in the direction of applied E while the negative charges will move away from applied E.

Electric field always moves from positive to negative , so the applied E can be imagined to be a strong array of positive charges at the bottom and a strong array of negative charges on the top. NOW it is easy to see why the bound charges get attracted the way they do.

B)

The electric dipole moments in the direction of E.

+ + ++ + +

Now that the bound charges have been polarized (positive charges towards E while the negative charges away from E) This will cause an induced dipole moment is always taken towards positive charge (in the direction of E)

C) The induced electric field (is very small) and will be always towards the negative charge.

+ + ++ +

At B, the components will cancel each other giving zero induced electric field (note: applied E is still present at B)

D) The polarization density (P) is defined such that it is in the direction of E.

E) Net pressure will be zero after the induced E is set up.