When the potential difference between the plates of a capacitor is increased by 4.21 V the magnitude of the charge on each plate increases by 20.1 µC. What is the capacitance of this capacitor?
__µF

I've no clue what to do here.... Ive tried solving for C using Q=CV and I'm way off...


any clues?

9/6/2007 9:15:42 PM

google.com

9/6/2007 9:39:35 PM

Check your units and try again.

9/6/2007 10:25:23 PM

I hate physucks... and I could be wrong, but here's my guess...

F = C/V

so uF = uC/V

So if the charge on each plate were to increase by 20uC when a potential difference between the plates of the capacitor is increased by 4V

then 20/4 = 5uF cap...

but I failed physucks 208...

9/6/2007 10:57:32 PM

Q=CV is exactly where you should start.

We'll turn this into simple Algerba.
State one: Q=CV
State Two: Q+20.1=C(V+4.21) I'm usually a units buff... but... right now I don't care
State Two simplified: Q+20.1=CV+C*4.21
State two minus state one: 20.1=C *4.21
Solve for C:
C=4.77 (microfarads or however you spell it)



Some days it's nice to know I still got it!!!

[Edited on September 8, 2007 at 8:59 AM. Reason : .]

9/8/2007 8:58:03 AM

bttt for another brain stumper

The current in an RL circuit increases to 79% of its final value 1.94 s after the switch is closed.
(a) What is the time constant for this circuit?


I know tau is L/R and I = (1-e^-tau/time)


please help!!!

9/27/2007 8:01:38 PM

it's a fucking algebra problem. stop being a douche and do your own homework.

9/27/2007 8:23:48 PM

nevermind. limpys right. i was over analyzing the hell out of this one. Once I rewrote it, I found it out pretty quick.

thanks anyway.

9/27/2007 9:29:09 PM