Part A

Charges on a metre stick

Two charges are stuck to a metre stick: a $+1\mathrm{.}0pC$ charge is stuck to the $0\mathrm{.}0cm$ mark, and a $-1\mathrm{.}0pC$ charge is stuck to the $10cm$ mark. Calculate the electrostatic potential at the $20\mathrm{.}0cm$ mark.