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Asked in GSEB Board July 2015 · Energy of a system of charges
Given: two electrons (like charges); their separation r decreases.
Idea: the potential energy of two point charges is U = (kq₁q₂)/r.
For two electrons q₁q₂ = (-e)(-e) = +e², so U = (ke²)/r is positive.
As r decreases, (ke²)/r becomes larger.
Physically, the approaching electron is slowed by the repulsion; the kinetic energy it loses is stored as potential energy of the pair.
So the potential energy of the system increases.
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