<p>If they even have biot-savart, I think I’d collapse.</p>
<p>EDIT: I just looked at the equation sheet, and biot-savart isn’t on there, but ampere’s law is. So, I don’t think they’d put us in a situation where we are forced to us biot-savart over ampere, right?</p>
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<p>This depends on the question…
If you have an expression for velocity, then find the maximum by setting its derivative equal to zero.
If its anything with springs then find when the KE is maximum, etc.</p>
<p>What a waste of time… :o</p>
<p>the circuits with /\ * | and -'s</p>
<p>How many points should I score in order to get a 4 or 5 ?</p>
<p>Question: I’m looking over a past test… there is a problem with a solenoid of n turns per length and with a current i. The first part asks to use ampere’s law to find the magnetic field near the center, and I get that. The second part asks to find the induced emf in a ring placed within the solenoid (so smaller radius), when the current decreases from i to t. So, I know I need to first find the flux through the smaller loop, but how exactly would I go about that? And then the third part asks to find the induced electric field at a point in the loop. How would I do that?</p>
<p>Changing current creates a change in the B-field (B=uni. Change in the B field leads to a change in flux (Ib=BA). Change in flux creates an induced emf = to -dIb/dt. Manipulate that a bit and you should get the right result (I think). For the third question, maybe E=-(vdr).</p>
<p>Also, what year was this?</p>
<p>They had a Biot-Savart on last years FRQ</p>
<p>Our teacher told us we didn’t have to worry bout Biot-Savart…</p>
<p>FUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU</p>
<p>Yeah, it was on the 2008 one. The ring of charge, right?
We did that as a test in-class, I did well. Thats one of the few things I get.
But if it shows up and its some other shape instead of a loop, I’m screwed.</p>
<p>So would the manipulations you are speaking of include finding the magnetic field that goes through the smaller ring, since we know the magnetic field that goes through the solenoid, so we’d just set up a ratio of areas of the two cross sections, right?</p>
<p>E=k<em>q</em>a/(x^2+a^2)^1.5, right? Where a is the ring’s radius and x is the distance from the center of the ring to the point. Do I need to know how to derive that?</p>
<p>^ yes I believe thats correct. I vaguely remember an equation like that for a loop inside a solenoid.
Well you have to show your work, you can’t just write that down.
So, technically, yes you need to know how to derive that.</p>
<p>Btw, anyone seen any problems with spherical capacitors?
Our teacher said there’s a high chance it might be on this year’s test or the next.</p>
<p>Lol k nvm, you just look at it as a spherical charge distribution and use the C = Q/V in differential form. Got it, got it.</p>
<p>Well, off to bed.
Good luck everyone!</p>
<p>Well for spherical capacitors if the distance between the plates is a lot smaller than its radius you can treat it like a parallel plate capacitor with Surface Area 4pir^2 right (for cylindrical i think you can) </p>
<p>That is one thing I am going to study.</p>
<p>As for the Solenoid think the current is I = nI or naI turns per length times length and then would be use b = u0 I / 2pir or am I totally forgetting everything lol.</p>
<p>As for the double integrals, they are much easier for me. I have a tendency to only retain newer information and we did those this year but not the integral building stuff. So I find it easier to use those, but they become complicated when you try to do Gauss’s Law (we did flux in Multivariable Calculus but not do to inverse square vector fields such as electric fields so they aren’t that easy for me to do with double integrals, but most other stuff is easier with Doubles.</p>
<p>You look at it as a spherical charge distribution then use Gauss’s Law and Find Electric Field then find potential and stuff?</p>
<p>Ugh can someone explain this graph? I have no clue how they got that.</p>
<p><a href=“Supporting Students from Day One to Exam Day – AP Central | College Board”>Supporting Students from Day One to Exam Day – AP Central | College Board;
<p>2d there</p>
<p>Here’s the question:
<a href=“Supporting Students from Day One to Exam Day – AP Central | College Board”>Supporting Students from Day One to Exam Day – AP Central | College Board;
<p>And uh… since no one answered my question earlier…
How do you deal with capacitors and resistors in parallel? Is the total current provided by a voltage source constant?</p>
<p>For which problem? the first one? nevermind 2 d doesn’t refer to dimension.</p>
<p>Well The capacitor starts off charged, so it seems like they ought to start off equal like the capacitor wasn’t even there. Then the Capacitor starts discharging. Wait this makes sense if they meant I1 to be across the capacitor. Then I2 starts off with all the current then as the capacitor discharges current through it exponential grows. Hmm maybe they mislabeled it.</p>
<p>For biot savarts law we just change dl so that it is r d theta for a circular piece of wire right so its dB = u0 I dl x r divided by 4pi r^2 and in infinite lengths of wire it collapses to u0 I/2pi r I think that shouldn’t be too bad then.</p>
<p>I am hoping this test goes pretty well, because I need to get a 5 (will get a 5) for colleges to look at the grades.</p>
<p>Good luck to everyone tomorrow.</p>
<p>Did I mention I hate Biot Savart?</p>
<p>How many of the formulas do we need to know for E+M. Would all the formulas on the formula sheet be enough?</p>
<p>Some of the formulas aren’t listed on there, like Biot Savart ( which I know I need to know), and some RC, RL and LC formulas.</p>
<p>For those who like to derive expressions, I think the formulas given on the sheet would be enough. But, a lot of stuff is just really easy, once you get the final equation. They don’t want to just give you the equation, so, yes, you are either expected to memorize it or know how to derive it based off of all the equations given. I don’t think there is anything that can not be derived from the given info, although biot-savart might be one of them.</p>
<p>I commend you feuxfollets. that takes some creativity. did you make a portfolio for Studio Art as well?</p>