I feel that my performance on Exam 1 is representative of my understanding of E&M at this point in time.
1. Strongly Agree
2. Agree
3. Neither Agree/Disagree
4. Disagree
5. Strongly Disagree
I feel that Exam 1 was a fair assessment.
1. Strongly Agree
2. Agree
3. Neither Agree/Disagree
4. Disagree
5. Strongly Disagree
I feel that Exam 1 was aligned with what we have been doing (in class and on homework).
1. Strongly Agree
2. Agree
3. Neither Agree/Disagree
4. Disagree
5. Strongly Disagree
## Announcements
* Goal: return graded Exam 1 by Monday
* Homework 6 Special problem 1 and 2
* Solve Exam 1 and turn into Danny on Friday
* Write a paragraph for each problem on what you needed to do to solve the problem correctly
* Ruxin will cover help sessions next week
The eletric field between the shells is just that of a point charge. What is the electric potential difference between the outer shell ($r=b$) and the inner shell ($r=a$)?
1. $\dfrac{Q}{4\pi\varepsilon_0}\left(\dfrac{1}{b}-\dfrac{1}{a}\right)$
2. $\dfrac{Q}{4\pi\varepsilon_0}\left(\dfrac{1}{a}-\dfrac{1}{b}\right)$
3. $\dfrac{Q}{4\pi\varepsilon_0}\left(\dfrac{1}{b^2}-\dfrac{1}{a^2}\right)$
4. $\dfrac{Q}{4\pi\varepsilon_0}\left(\dfrac{1}{a^2}-\dfrac{1}{b^2}\right)$
5. Something else?
Note: Correct Answer is B
What is the sign of the potential difference between the outer shell ($r=b$) and the inner shell ($r=a$)?
$\Delta V = V(b) - V(a)$
1. $\Delta V > 0$
2. $\Delta V < 0$
2. ???
Note: Correct Answer is A
<img src="./images/capacitor_gap_bigger.png" align="right" style="width: 300px";/>
You have two very large parallel plate capacitors, both with the same area and the same charge $Q$.
Capacitor \#1 has twice the gap of Capacitor \#2. Which has more stored potential energy?
1. \#1 has twice the stored energy
2. \#1 has more than twice
3. They both have the same
4. \#2 has twice the stored energy
5. \#2 has more than twice.
Note:
* CORRECT ANSWER: A
* E same; twice volume
<img src="./images/capacitor_gap_connected.png" align="center" style="width: 500px";/>
A parallel plate capacitor is attached to a battery which maintains a constant voltage difference V between the capacitor plates. While the battery is attached, the plates are pulled apart. The electrostatic energy stored in the capacitor
1. increases.
2. decreases.
3. stays constant.
Note:
* CORRECT ANSWER: B
* Potential same; field is reduced; but shows up squared while d is increased, overall goes down
### Laplace's Equation
<img src="./images/laplace.png" align="center" style="width: 900px";/>
<img src="./images/region_w_no_charge.png" align="right" style="width: 200px";/>
A region of space contains no charges. What can I say about $V$ in the interior?
1. Not much, there are lots of possibilities for $V(r)$ in there
2. $V(r)=0$ everywhere in the interior.
3. $V(r)=$constant everywhere in the interior
Note:
* CORRECT ANSWER: A
<img src="./images/region_with_no_charge_Vset.png" align="right" style="width: 200px";/>
A region of space contains no charges. The boundary has V=0 everywhere.
What can I say about $V$ in the interior?
1. Not much, there are lots of possibilities for $V(r)$ in there
2. $V(r)=0$ everywhere in the interior.
3. $V(r)=$constant everywhere in the interior
Note:
* CORRECT ANSWER: B