Scaling factor of Energy in a capacitor with change in charge

[mrcotton]

Homework Statement

AQA Section A Q18 Jun 11

Homework Equations

The answer should be C

E=.5QV and C=Q/V

The Attempt at a Solution

So the original Q has increased by 1.5 times If C is constant than the voltage must also increase by 1.5 times

Now the energy E is E=.5QV V has increase by 1.5 and and so has Q which is 2.25

Infact in typing this out I think I just solved it. Is this logic and method ok

 

[Dick]

Homework Statement

AQA Section A Q18 Jun 11

Homework Equations

The answer should be C

E=.5QV and C=Q/V

The Attempt at a Solution

So the original Q has increased by 1.5 times If C is constant than the voltage must also increase by 1.5 times

Now the energy E is E=.5QV V has increase by 1.5 and and so has Q which is 2.25

Infact in typing this out I think I just solved it. Is this logic and method ok

Seems fine to me.

 

[jfgobin]

Yup. You may recall that the energy stored in a capacitor is also given by:

$E = \frac{1}{2}CV^2$
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