RC circuits on MCAT?????????

[chemsmith]

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Hi fellow MCAT-induced anxiety suffers,

Does anyone have a good idea of what we are expected to know concerning RC circuits? I was using examkrackers but their electricity and magnetism lecture was really really weak so I went over E&M again with nova. The aamc topic lists includes "discharge of a capacitor through a resistor" but neither EK, Kaplan, nor Nova covers RC circuits. Whats up with that? Time to break out the physics tome?

 

[macsta]

Hi fellow MCAT-induced anxiety suffers,

Does anyone have a good idea of what we are expected to know concerning RC circuits? I was using examkrackers but their electricity and magnetism lecture was really really weak so I went over E&M again with nova. The aamc topic lists includes "discharge of a capacitor through a resistor" but neither EK, Kaplan, nor Nova covers RC circuits. Whats up with that? Time to break out the physics tome?

RC is just a resistor and capacitor circuit. I'm sure you don't need to know that much detail about it...just know the basics. Capacitor discharge is just that one forumla like V(t) = Vo [1-e^(t/

&#964😉].

 

[MT Headed]

EK 1001 physics has many RC circuit problems. They are all of the conceptual nature, which is all that is likely to appear on the MCAT too. I don't remember seeing a single RC circuit on any of the publicly available AAMC CBT's.

Granted I've never taken an actual MCAT, but it doesn't seem the sort of place where they would blindly ask you for the exact current after 5 seconds (the way a physics textbook would).

Just know they charge fast and then taper off, they discharge fast and then taper off, and they are kind of like a lousy battery. Know the shape of a current vs time or charge vs time for various scenarios. That's about it.

 

[chemistryguy]

I've never seen any quantitative question on RC circuits on a practice test. However, you should know what the current versus time graph for charging and discharging looks like (its an exponential!). You should also know whats happening at each point while charging and discharging conceptually, which is probably much more important than simply memorizing the equations.

 

[movax]

Only one I remember on a practice test had conceptual questions pertaining to what the voltage across the plates looked like whilst the capacitor discharged. It's pretty standard stuff. You don't need to know the calculus like I = C * dv/dt and such.

If you're not electrically-inclined, you could always apply the water analogy to it I suppose.

e: I have never seen inductors or inductance show up once, don't worry about L.

 

[whiteshadodw]

EK 1001 physics has many RC circuit problems. They are all of the conceptual nature, which is all that is likely to appear on the MCAT too. I don't remember seeing a single RC circuit on any of the publicly available AAMC CBT's.

Granted I've never taken an actual MCAT, but it doesn't seem the sort of place where they would blindly ask you for the exact current after 5 seconds (the way a physics textbook would).

Just know they charge fast and then taper off, they discharge fast and then taper off, and they are kind of like a lousy battery. Know the shape of a current vs time or charge vs time for various scenarios. That's about it.

SPOILER ALERT.
*****
*****
*C*B*T*#***
*******
*****
****
/spoiler

lol i didn't give it away. but its on one of the CBTs, if only making a brief cameo for like a question, but involved in a whole passage. if its on the official AAMC topics list assume its gonna be on the MCAT.

i would also know that a fully charged capacitor impedes the flow of current more than an uncharged capacitor. also, be aware that a polarized cell is essentially a capacitor just waiting to be discharged (depolarization = action potentional)