Predict the results of the following experiment: a paramagnetic bar and a diamagnetic bar are pushed inside of a solenoid.
1. The paramagnet is pushed out, the diamagnet is sucked in
2. The diamagnet is pushed out, the paramagnet is sucked in
3. Both are sucked in, but with different force
4. Both are pushed out, but with different force
Note:
* CORRECT ANSWER: B
## Announcements
* Final Exam!
* 12:45-2:45pm, Tues Dec. 12
* In this room (1415 BPS)
## What's on the final exam?
* A few true/false questions about $\mathbf{B}$, $\mathbf{H}$, and Ampere's Law
* Determine bound charge, $\mathbf{E}$, $\mathbf{D}$ for some material ($\mathbf{P}$), and explain how quantities might change
* Determine and explain the direction of the force between two dipoles in some configuration
* Determine the $\mathbf{B}$ for some $\mathbf{J}$
* Determine bound currents, $\mathbf{B}$, and $\mathbf{H}$ for some material with a "simple" free current, and explain properties of the bound currents
A very long aluminum (paramagnetic!) rod carries a uniformly distributed current $I$ along the $+z$ direction.
What is the direction of the bound volume current?
<img src="./images/Al_rod_example_current_shown.png" align="right" style="width: 200px";/>
1. $\mathbf{J}_B$ points parallel to $I$
2. $\mathbf{J}_B$ points anti-parallel to $I$
3. It’s zero!
4. Other/not sure
Note:
* CORRECT ANSWER: A
A very long aluminum (paramagnetic!) rod carries a uniformly distributed current $I$ along the $+z$ direction. We know $\mathbf{B}$ will be CCW as viewed from above. (Right?) What about $\mathbf{H}$ and $\mathbf{M}$ inside the cylinder?
<img src="./images/Al_rod_example_B_shown.png" align="right" style="width: 200px";/>
1. Both are CCW
2. Both are CW
3. $\mathbf{H}$ is CCW, but $\mathbf{M}$ is CW
4. $\mathbf{H}$ is CW, $\mathbf{M}$ is CCW
5. ???
Note:
* CORRECT ANSWER: A
A very long aluminum (paramagnetic!) rod carries a uniformly distributed current $I$ along the $+z$ direction. What is the direction of the bound volume current?
<img src="./images/Al_rod_example_HBM_shown.png" align="right" style="width: 200px";/>
1. $\mathbf{J}_B$ points parallel to $I$
2. $\mathbf{J}_B$ points anti-parallel to $I$
3. It’s zero!
4. Other/not sure
Note:
* CORRECT ANSWER: A
A very long aluminum (paramagnetic!) rod carries a uniformly distributed current $I$ along the $+z$ direction. What is the direction of the bound surface current?
<img src="./images/Al_rod_example_current_shown.png" align="right" style="width: 200px";/>
1. $\mathbf{K}_B$ points parallel to $I$
2. $\mathbf{K}_B$ points anti-parallel to $I$
3. Other/not sure
Note:
* CORRECT ANSWER: B
For linearly magnetizable materials, the relationship between the magnetization and the H-field is,
$\mathbf{M} = \chi_m \mathbf{H}$
What do you expect the sign of $X_m$ to be for a paramagnetic/diamagnetic material?
1. para: $\chi_m<0 \;$ dia: $\chi_m>0$
2. para: $\chi_m>0 \;$ dia: $\chi_m<0$
3. Both positive
4. Both negative
Note:
Correct answer: B