Potential Energy - Single Particles/Systems If we have two charged particles in an electric field, then there is a potential energy in the system. 
I am aware that it is meaningless to talk about the potential energy of a single particle alone. However,what about the phrase 'potential energy of charge $q_1$ due to $q_2$', for example, does that make sense?
I just need a bit of elucidation on the phrasing we use when we talk about potential energy (and some explanation of why would be appreciated).
 A: Imagine it this way (strictly intuitive and physical):


*

*If both charges 1 and 2 are positive, there will be some repulsive force between the two, i.e. charge 2 gets repelled owing to the presence of the charge 1 and vice versa. 

*In case the latter was absent, there would be no such force.

*With both these charges present, there would also be some energy of interaction. Imagine this as a manifestation of the force, if the force "pushes" the other charge away, its energy also increases. Notably, this energy wouldn't have "existed" if the other charge was missing, so this is really "due to the presence of the other charge". 

*When you set up any charge configuration, e.g. a system of 100 electrons (i.e. 100 units negative charge) on a conducting sphere, you are doing work against this repulsive force, and therefore expending certain amount of energy in setting up this charge configuration. e.g. when you add the first electron, there's no problem, but the second electron experiences a repulsion because the first one is already present there earlier. Likewise, the third experiences even more, there are two electrons repelling it, and so on.
This is the physical meaning of the potential energy of $q_1$ due to $q_2$, or rather, the potential (energy) of any system of charges.
