<p>@ Ramblinman</p>
<p>“Don’y worry too much, last year I thought that I bombed it, but I got 5s on both sections. I’m sure most of the people on this site will get 4s and 5s.” </p>
<p>What percentage of the FR and MC for each section did you think you got right?</p>
<p>I think I got around 35-40% right on the FR and 70-80% right on the MC.</p>
<p>For E&M 3, you were supposed to used Ampere’s Law to find B (or just memorize the magnetic field due to a long wire).Then integrate once more to find the flux.</p>
<p>Does anyone remember if the last part of E&M3 was asking for energy or power?</p>
<p>@christiansoldier - don’t worry about it - the curves are usually very generous. I know someone who pretty much left 2 FR blank and still got a 5.</p>
<p>@Esplin - I had no idea what I was doing for E&M 3, so I just plugged in my answer from Ampere’s to find the flux, and used d and d+a as the bounds of integration. I still have don’t know how time comes into the equation though.</p>
<p>For E&M 1, you have to integrate the dq’s from 3pi/4 to 5pi/4… because you only want the cosines. And I thought C had the highest potential and A & B tied for second.</p>
<p>@iceui time came into the equation because B for a long wire has current in its expression, and they gave you current as a function of time, so just plug it in</p>
<p>@JDong</p>
<p>I’m pretty sure it was power</p>
<p>@iceui2</p>
<p>Time comes from the current equation they gave you.</p>
<p>Jdong, could you explain that more fully?</p>
<p>Iceui, I think you could infer that all the vertical components canceled and then put a cos next to the Electric field strength. Atleast that’s what I did.</p>
<p>But to find the flux… wouldn’t you have to integrate it with respect to y? (since phi = integral of B dA)</p>
<p>Jdong, could you explain that more fully?</p>
<p>Iceui, I think you could infer that all the vertical components canceled and then put a cos next to the Electric field strength. Atleast that’s what I did.</p>
<p>B was whatever the formula for magnetic field due to a long wire is (too lazy to look it up and don’t remember it by heart). it’s like a bunch of constants divided by 2pi<em>r. All of the constants could be brought out front of the integral, except for the r in the denominator since the differential area dA was b</em>dr. I had the same limits of int. as you, and my answer had a natural log in it</p>
<p>the mechanics MC destroyed me…grrr…</p>
<p>My answer also had a natural log in it, and that scared me a little…</p>
<p>I thought we had to use the Biot-Savert formula : (</p>
<p>does it goes dimmer or wat?? for E&M</p>
<p>For E&M 3: You can use Biot-Savert to get the magnetic field (or Ampere’s).</p>
<p>But to get the flux, I think you have to use the equation Flux = integral of B dA.</p>
<p>Plug in B from the previous part… but using I-kt for the new I. Then convert dA to length * dy. The bounds of integration is d to d+a.</p>
<p>You should get a natural log in the answer, but I wasn’t even sure if I set up the integral right so I didn’t actually integrate it.</p>
<p>I’ve done tons of practice for Mech (the only one I took), and I’m pretty sure I’ve never seen anything as hard. The multiple choice was a lot more complex than previous years’. The Free Response: not terribly bad, but still a lot harder. I didn’t finish the MC for the first time ever. So, assuming that more people thought of it as a total ass-kicking, the curve will be high? Please let it be high.</p>
<p>Oh, that makes sense. </p>
<p>So, then for the last part, did we have to take the integral of the function of I and plug it into a power formula?</p>
<p>i finished with time to spare on both the mc and frq’s… but then again, i’m totally mindf***ed right now and dgaf anymore 
plus, i played “frq fail bingo” for about 30 minutes, haha. probably the hardest test ive taken, plus i didn’t take e&m, so i didn’t have all that floating around in my head… at best a 3…at best.</p>
<p>"So, then for the last part, did we have to take the integral of the function of I and plug it into a power formula? "</p>
<p>I took the deerivative of the flux function to find the induced emf, them used P = V^2 / R</p>
<p>^^ Nice… should’ve thought of that :)</p>
<p>From what people are saying it sounds like we were supposed to use a lot of calculus in the FRQ’s for Mech. Thank god my school allows juniors who havn’t taken Calculus yet into a physics class making it so the teacher never teaches us the way to do anything using Calculus so that nobody in the class is at a disadvantage. Juniors didn’t even learn integrals in Calculus until April. I think we spent a day trying to learn every calculus aspect of Physics minus derivative stuff. I definitely got a 2…■■■</p>