# kd2eom

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1. ## AP Physics C 2017 E&M Free Response

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2. ## AP Physics C E&M Question

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3. ## Another AP Physics C E&M Question

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4. ## AP Physics C 2017 E&M Free Response

I just watched this APlusPhysics video: https://www.youtube.com/watch?v=1wAwkyzxB0k I have a question for 2. a. Why is voltage across C0 equal to V0? I understand how this be the case if the resistor R1 was not there (since voltages are the same for components connected in parallel); however, since the resistor is connected to the capacitor in series, wouldn't the voltage V0 be split across C0 and R1 (which means C0 would have a voltage less than V0)?﻿ Also, for 2. b - I originally thought that I2 would increase, because when the switch is first closed, the capacitor acts like a wire and allows current to flow freely, so the current will be split between both the R1 and R2 parallel branches. Then, after a long time, the capacitor acts like an open switch, so no current will flow through R1 and it will all flow through R2 - therefore, the current in R2 would increase. After watching this video, I understand Mr. Fullerton's reasoning as to why I2 remains constant, but I'm not sure what was wrong with my original thinking. Thank you for any help!
5. ## Another AP Physics C E&M Question

Hello, This question features a circuit with a resistor, an inductor, and a battery all connected in series. It then shows an increasing concave down graph of something vs. t - the graph started at the origin and had a horizontal asymptote at some positive value of x. The "something" could be: A. The potential difference across the resistor B. The potential difference across the inductor and/or C. The current in the circuit. I had reasoned that it would be all 3. When an inductor is first connected to a battery at time t=0, it doesn't allow electricity to flow, but as time goes on, it allows more and more electricity to flow until it is essentially acting like a wire. Therefore, current will increase, and voltage will also increase across the entire circuit. However, it turned out that B was incorrect, and I'm not sure why (I eventually received the answer to this question but not the explanation). Why is this the case? Thank you!
6. ## AP Physics C E&M Question

Hi, I'm confused about this question: "A proton is moving to the right at constant speed v and enters a region with uniform magnetic and electric fields. It continues to move in a straight line. The magnetic field is directed toward the top of the page. What is the direction of the electric field?" Using the right hand rule, with fingers pointed to the right and curled fingers up, my thumb points out of the page, leading me to believe that would be the answer. The correct answer is actually that the electric field points into the page. Why is this? Thank you!