Two point charges, q1 = +8.0 μC and q2 = -2.0 μC, are placed 0.40 m apart in vacuum. What is the electric potential at the midpoint between the charges? (Use k = 9.0 × 10^9 N·m^2/C^2)
Show the answer and explanation
Correct answer
A. 2.7 × 10^5 V
Principle or equation
Electric potential due to a point charge is V = kq/r. The net potential at a point is the algebraic sum of the potentials from each charge.
Why this answer is correct
Midpoint is 0.20 m from each charge. V1 = (9e9)(8e-6)/0.20 = 3.6e5 V. V2 = (9e9)(-2e-6)/0.20 = -9.0e4 V. Net V = 3.6e5 - 9.0e4 = 2.7e5 V.
Example
For q1 = +4 μC and q2 = -1 μC separated by 0.20 m, midpoint potential = k(4e-6)/0.10 + k(-1e-6)/0.10 = 3.6e5 - 9e4 = 2.7e5 V.
This published item includes a stored explanation and passed the platform’s publication workflow. It is independent preparation material, not a claim of an official or recalled examination question.