80. (a) The charges are equal and are the same distance fromC. We use the Pythagorean theorem to Fndthe distancer=p(d/2)2+(d/2)2=d/√2. The electric potential atCis the sum of the potentialdue to the individual charges but since they produce the same potential, it is twice that of eitherone:V=2q4πε0√2d=2√2q40d=(8.99×109N·m2/C2)(2)√2(2.0×10−6C)0.020 m=2.54×106V.(b) As you move the charge into position from far away the potential energy changes from zero toqV,whereVis the electric potential at the Fnal location of the charge. The change in the potentialenergy equals the work you must do to bring the charge in:W==(2.0×10−6C)(
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