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