A square of side 0.20 m has identical point charges +Q fixed at each of its four corners
PHYSICS · Multi-part · CBSE · Physics · Electric Charges and Fields · Electric Charges and Fields
Problem
A square of side 0.20 m has identical point charges +Q fixed at each of its four corners. A small positive test charge q is placed at the geometric center of the square. Air resistance and gravity are negligible.
(a) Describe the magnitude and direction of the net electric force acting on the test charge when it is exactly at the center. Provide a qualitative justification based on symmetry.
(b) The test charge is displaced a small distance toward the lower-right corner while remaining inside the square. Qualitatively describe the new direction of the net electric force on the displaced charge and state whether its magnitude becomes larger, smaller, or remains the same compared with part (a). Explain your reasoning.
(c) The charge at the upper-left corner is replaced by a charge −Q (same magnitude, opposite sign). After the replacement, the test charge is returned to the center of the square. Predict the direction of the net electric force on the test charge and state whether the magnitude of the force is zero or non-zero. Justify your answer using superposition and symmetry arguments.