RC Circuits - Review for AP Physics C: Electricity and Magnetism

[@ethanmoilanen9811]

Thank you so so much for the hard work you put into these videos and trying to get these vids out before the exam. I know they take forever to make but the niche community of AP Physics E&M students really appreciate it!

[@FlippingPhysics]

Glad you appreciate it!

[@yinvara]

You put in so much work it's criminally underrated. I share when I can

[@OkOk-ug5ct]

Thank you for these videos, very much appreciated. Lots of love towards the team

[@RoRo-we4ev]

dude i love you T_T, hope you're aware how great you are

[@user-ng4lm1ir2b]

4:08 why do we charge a capacitor through resistor?

[@mr.austinhailubasinger7822]

Loved the reference to The Doors!

[@FlippingPhysics]

Thanks. I'm learning that most people did not get the reference. Oh well!

[@johnnichols6073]

I usually teach "a long time later" as meaning 5-10+ time constants, since 5RC gets the circuit 99.5% of the way to its final value. But you haven't discussed time constant yet, so this seems absolutely fine in this case.

[@FlippingPhysics]

Yeah. I decided could have returned to that after I introduced the time constant, however, it seemed logical just to leave it that way.

[@physicslab5787]

Great explanation

[@rishavjain5087]

thanku very much

[@TheCosmicGuy0111]

Thanks!

[@eljison]

Good job! I didn't realize that we could use "asymptotes" as a verb. I guess it is easier than saying "asymptotically approaches". Does the AP Physics C include realistic batteries (with internal resistance), or account for having more than one resistor in the circuit? We include them in University Physics courses.

[@FlippingPhysics]

Yes, AP Physics C: Electricity and Magnetism includes batteries with internal resistance and circuits with multiple resistors in them. Thanks for previewing!

[@johnnichols6073]

Nice! I usually have students ask about the absolute value in the integral of 1/x and why we don't use it in this derivation. Do you normally address this when going through this for the first time?

[@FlippingPhysics]

That's funny. I do not recall a student ever asking that question. How would you answer it?

[@johnnichols6073]

@@FlippingPhysics It depends on how much time I have and when it is in the year. They particularly don't like the denominator. One approach is "I know there's the absolute value, but we're going to ignore it. I've done this before, and it's fine in this situation." Not very satisfying, but certainly quickest. The alternate approach is that q-εC actually is a negative number in this approach, since q initial is 0 C, so we actually need the negative on the bottom for the whole fraction to be positive.

[@FlippingPhysics]

That all makes sense. Thanks. At this point I do not see a reason to add anything to the video.

[@drkaplan2]

The derivation does not deal with the absolute value ln|x+a|. I note that most people who present this leave it out, but it needs to be addressed. In this case x (or q) is ALWAYS less than a (or Eps C), so the items inside the absolute the absolute value are always negative. Therefore, the ln|x-a| = ln(a-x). Therefor the integral is in face ln(a/x).

[@mikeytodorov134]

@20:18 did we just get some flipping lore??

[@ronaksamani2807]

Fantastic. Will you do one for RL Circuit?

[@wizwilzo]

ap test is in 3 days, this owuld help a lot too but dont rush it!

[@skylerpretto1221]

I wish more physics videos had Doors references. 😛

[@FlippingPhysics]

So true