Potentail Energy beyond infinity

[Ali Asadullah]

I read in a book that if an electron is beyond infinity from another charge particle,
then its potential energy will be positive :/
Please tell me which formulae are used for potential energy beyond infinity??

 

[dulrich]

There is no such thing as beyond infinity. Truly, there is no such thing as having the electron at infinity either. It's just a short-hand way of saying suppose you separate the electron far, far away without limit.

 

[Ali Asadullah]

Then at what position, an electron will have positive potential energy?

 

[dulrich]

The potential energy of a charge is the product of its charge and the electric potential in which it sits: PE = qV. Since the charge of an electron is negative, if the electric potential around it is negative, the potential energy will be positive. If another negative charge is around, its electric potential will be negative. So the potential energy between two charges of the same sign will be positive.