Question

In the picture below, the 3 charges Q₁, Q₂and Q₃ are located at positions (-a,0), (a,0) and (0,-d) respectively.
(The origin is the point halfway between Q₁ and Q₂.)

Consider the special case where Q₁, Q₃greater than zero and Q₂ = -Q₁.
Select true or false for each statement.
True False  If Q3 is released from rest, it will initially accelerate to the right.
True False  The electric potential at any point along the y-axis is positive.
True False  The electric potential at the origin equals Q3/(4πε₀d).
(Here k = 1/(4πε₀))
True False  The work required to move Q3 from its present position to the origin is zero.
True False  The electric field at the origin pointssolely in the positive y direction.
True False  The force on Q3 due to the other two charges is zero.
True False  The external work done to bring these charges to this configuration (from infinity) was positive.

b) In the previous problem, let Q₁=1.50 μC, Q₂=-3.20 μC, and Q₃=3.50 μC. (Note that Q₁ and Q₂ are different now.) The distances are a=1.20 cm and d=2.80 cm.
Calculate the potential energy of the charge configuration

Answer 1