Parallel capacitor, electrostatic energy

[dinhjeffrey]

Homework Statement

if the separation between the plates of an isolated charged parallel-capactior is increased, why does the stored electrostatic energy increase?

Homework Equations

C=eA/d
e= permitivity of space

The Attempt at a Solution

i do not know the equation of electrostatic energy, is it E = (1/4πεo)Q/r2?
if so, then if distance increase, the radius in this here equation would increase therefore the electrostatic energy should be lowered?

 

[tiny-tim]

hi dinhjeffrey!

if the separation between the plates of an isolated charged parallel capacitor is increased, why does the stored electrostatic energy increase?

hint: what do we have to do to increase energy?

 

[dinhjeffrey]

hi dinhjeffrey!


hint: what do we have to do to increase energy?

wait which formula is for electrostatic energy again? i get all the electric formulas mixed up ><

 

[tiny-tim]

does the formula matter?

what do we have to do to increase energy?

 

[dinhjeffrey]

does the formula matter?

what do we have to do to increase energy?

umm do we increase temperature? i am really bad at physics ><

 

[ojs]

First you have to know what electrostatic energy is, look that one up in wikipedia for instance (use all the resources at your disposal, search the net, look through your books, then ask questions).
How does the electrostatic energy change when the distance between the plates in a parallel plate capacitor is changed?
Can you find the answers to these questions?

 

[dinhjeffrey]

First you have to know what electrostatic energy is, look that one up in wikipedia for instance (use all the resources at your disposal, search the net, look through your books, then ask questions).
How does the electrostatic energy change when the distance between the plates in a parallel plate capacitor is changed?
Can you find the answers to these questions?

yeah i was confused when i googled it because i thought electrostatic energy isn't the same as electric potential energy.
oh okay i think i get it. is it because PE=-qe⌂x, so if you increase distance, PE(electrostatic energy) increase too?

 

[ojs]

Correct! You solved your problem :-)

 

[tiny-tim]

why not just use change in energy = work done ?

do we have to do work to bring the plates nearer, or further apart? ​