Capacitors: find he charge for the new battery

[Alice7979]

Homework Statement

A capacitor stores 7.9 x 10-2 C of charge when connected to a 6.0-V battery. How much charge does the capacitor store when connected to a 9.0-V battery?

Homework Equations

PE=CQ/2

The Attempt at a Solution

QV^2=CQ^2
(7.9 x 10-2)(6)/2 = Q(9)
C= .05 C

 

[David Lewis]

You are looking for an equation that relates capacitance, charge held on the plates, and the voltage across the plates.
1. Solve for capacitance.
2. Rearrange the equation and solve for charge.

 

[scottdave]

This site should help you relate Voltage, Capacitance and Charge. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capac.html

 

[Alice7979]

I guess I made that more complicated

 

[David Lewis]

If you want to post the answer you came up with, I will see if it matches mine.

 

[Alice7979]

.1185 C

 

[David Lewis]

That's what I got. The precision of the given data is 2 significant figures, so I rounded to 0.12 C.