Two identical point charges each are placed apart in air

PHYSICS · Single correct · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

Two identical point charges

+1\,\mu\text{C}

each are placed

30\,\text{cm}

apart in air. Calculate the work that must be done to increase their separation to

90\,\text{cm}

, assuming the process is carried out slowly so that kinetic energy changes are negligible. (a)

+2.0\times10^{-2}\,\text{J}

(b)

-4.0\times10^{-2}\,\text{J}

(c)

-2.0\times10^{-2}\,\text{J}

(d)

-1.0\times10^{-2}\,\text{J}