Charge flowing through a capacitor

[aliaze1]

Homework Statement

Initially, the switch in the figure is open and the capacitor is uncharged.

How much charge flows through the switch after the switch is closed?

Homework Equations

Q = C*ΔV_C

The Attempt at a Solution

Using the given values:

Q = (10*10^-6) * 1.5 = 1.5*10^-5

which is incorrect..

in another calculation i got 1.5*10^-4, also incorrect

any help?

thanks!

 

[dynamicsolo]

In what way is 1.5·10^-5 C incorrect? When the capacitor is fully charged, the voltage across it equals the battery voltage; the charge will be Q = CV_batt . Since the capacitor started out uncharged, that should be the amount of charge that flowed through the switch on its way to the positive plate.

Is this a problem on a computer system like WebAssign? Is your statement of the problem exactly what was asked? The reason I ask this is that I've worked with students who had to use systems like this in the past; one of the reasons they often had answers rejected was because they weren't answering the question as stated. One of those reasons was that they weren't using the requested units. Do they want the answer in Coulombs, or perhaps in microcoulombs?

 

[aliaze1]

yea its MasteringPhysics

i forgot to mention that it asks for microcoulombs

 

[aliaze1]

aaahhhhhhhhh you are right! it was the UNITS! LOL i was putting it in as Coulombs instead of microcoulombs

THANKS!

 

[Vidatu]

Answered before I got here...

 

[dynamicsolo]

aaahhhhhhhhh you are right! it was the UNITS! LOL i was putting it in as Coulombs instead of microcoulombs

THANKS!

I thought it might be something going on like that. Be very careful in working with inputs to the questions; read the problem statements closely. Every dang problem on those systems is like taking a multiple choice test -- you get no credit for doing the problem correctly if you don't answer it just right! (Computers are stupid like that...)