Where the energy to move electroscope leaves comes from?

[alikim]

Hi,

My question is about gold-leaf electroscope induction experiment as it's shown here: http://en.wikipedia.org/wiki/File:Electroscope_showing_induction.png

To spread out leaves you need to spend some energy, I'd like to know where it comes from

Thank you!

 

[tiny-tim]

welcome to pf!

hi alikim! welcome to pf!

the hand (in the picture) has to do more work to bring a charged rod near the plate than if the rod was not charged …

the extra energy is supplied by the hand

(which i assume is attached to a live human )

 

[alikim]

Thanks heaps!

 

[DrZoidberg]

If the electroscope is uncharged then the rod will be attracted to it and that means it takes less work to move a charged rod near the plate then an uncharged rod.
The energy comes from the electric charge and the voltage. Electric energy is charge times voltage.