A small chunk of material (the “tan cube”) is placed above a solenoid. It magnetizes, weakly, as shown by small arrows inside.
What kind of material must the cube be?
<img src="./images/tan_cube_magnetization.png" align="right" style="width: 300px";/>
1. Dielectric
2. Conductor
3. Diamagnetic
4. Paramagnetic
5. Ferromagnetic
Note:
* CORRECT ANSWER: C
## Announcements
* 3 Classes left!
* Today and Wednesday: normal lecture (finish Ch. 6)
* Friday: conceptual assessment
* Participation? Drop second lowest homework grade
* Final Exam
* Thursday 12:45-2:45pm in this room
* Details on Friday!
A solid cylinder has uniform magnetization $\mathbf{M}$ throughout the volume in the $x$ direction as shown. What's the magnitude of the total magnetic dipole moment of the cylinder?
<img src="./images/M_in_x_cylinder.png" align="right" style="width: 200px";/>
1. $\pi R^2 L M$
2. $2\pi R L M$
3. $2\pi R M$
4. $\pi R^2M$
5. Something else/it's complicated!
Note:
* CORRECT ANSWER: A
<img src="./images/M_in_z_cylinder.png" align="right" style="width: 200px";/>
A solid cylinder has uniform magnetization $\mathbf{M}$ throughout the volume in the $z$ direction as shown. Where do bound currents show up?
1. Everywhere
2. Volume only, not surface
3. Top/bottom surface only
4. Side (rounded) surface only
5. All surfaces, but not volume
Note:
* CORRECT ANSWER: D
<img src="./images/M_in_x_cylinder.png" align="right" style="width: 200px";/>
A solid cylinder has uniform magnetization $\mathbf{M}$ throughout the volume in the $x$ direction as shown. Where do bound currents show up?
1. Top/bottom surface only
2. Side (rounded) surface only
3. Everywhere
4. Top/bottom, and parts of (but not all of) side surface (but not in the volume)
5. Something different/other combination!
Note:
* CORRECT ANSWER: D
<img src="./images/M_in_phi_cylinder.png" align="right" style="width: 200px";/>
A solid cylinder has uniform magnetization $\mathbf{M}$ throughout the volume in the $\phi$ direction as shown. In which direction does the bound surface current flow on the (curved) sides?
1. There is no bound surface current.
2. The current flows in the $\pm \phi$ direction.
3. The current flows in the $\pm s$ direction.
4. The current flows in the $\pm z$ direction.
5. The direction is more complicated.
A sphere has uniform magnetization $\mathbf{M}$ in the $+z$ direction. Which formula is correct for this surface current?
<img src="./images/sphere_uniform_M.png" align="right" style="width: 300px";/>
1. $M \sin \theta\,\hat{\theta}$
2. $M \sin \theta\,\hat{\phi}$
3. $M \cos \phi\,\hat{\theta}$
4. $M \cos \phi\,\hat{\phi}$
5. Something else
Note:
* CORRECT ANSWER: B