A student models the region of space surrounding two identical point charges fixed in…
PHYSICS · Multi-part · CBSE · Physics · Electric Charges and Fields · Electric Charges and Fields
Problem
A student models the region of space surrounding two identical point charges fixed in place. She reports that all points that are 12 cm from the midpoint between the charges and lie on the line joining the charges are at +150 V, while all points that are 12 cm from the midpoint and lie on the perpendicular bisector of the line joining the charges are at +75 V. She sketches several equipotential curves and marks three specific locations:
• Point P lies on the perpendicular bisector, 6 cm above the midpoint.
• Point Q lies 6 cm to the right of the midpoint along the line joining the charges.
• Point R lies 6 cm below the midpoint on the perpendicular bisector.
Assume no other charges are present.
(1) Identify whether the fixed point charges are positive, negative, or of opposite sign. Justify your answer using the given potentials.
(2) For each point P, Q, and R, state the direction of the electric field vector (toward the midpoint, away from the midpoint, upward, downward, leftward, or rightward). Explain your reasoning based on the relationship between electric field direction and electric potential.
(3) Explain why moving a small test charge from point P to point R along the perpendicular bisector requires no work, even though the path passes near the charges.