Question

Three point objects have electrical charges and locations, as shown in the figure below to the left.
(a) Calculate the electrical potential energy U for this three-charge system.
(b) Calculate the electric potential V due to this three-charge system at a point 10.0 cm
directly above the 3.00 μC charge.

Answer 1

As the question image is missing,

So I am taking an assumption that there is 3 equal positive charges are situated at the vertices of the triangle. The magnitude of the charges are $q\mu C$ .and let the length of the side of the triangle is a cm.

a) So electric potential energy of the system = $\dfrac{q^2}{4\pi \epsilon_o a}+[\dfrac{q}{4\pi \epsilon_o a}-\dfrac{q}{4\pi \epsilon_o a}]$

Hence net electric potential energy due to the system$=\dfrac{q^2}{4\pi \epsilon_o a}$

b)Now point is just above the one vertices which have the charge = $3\mu C$ at 10cm above.

$=\dfrac{3q}{4\pi \epsilon_o \sqrt{a+10^2}}+\dfrac{3q}{4\pi \epsilon_o \sqrt{a+10^2}}+\dfrac{3q}{4\pi \epsilon_o 10}-\dfrac{3q}{4\pi \epsilon_o a}$

$=\dfrac{6q}{4\pi \epsilon_o \sqrt{a+10^2}} +\dfrac{3q}{4\pi \epsilon_o 10}-\dfrac{3q}{4\pi \epsilon_o a}$

As the diagram is missing, so i solved it as per the assumption.