Charges +Q, −Q, +Q, −Q at corners of a square (side 5 cm). Find field at centre. (Q = 1 μC)
PhysicsClass 11CBSEAnswered 22 May 2026
Answer
With alternating charges, the two +Q charges are at diagonally opposite corners, and the two −Q charges are at diagonally opposite corners.
Field at centre from each pair:
Both +Q fields: exactly opposite directions ⇒ cancel
Both −Q fields: exactly opposite directions ⇒ cancel
Every field vector has an equal and opposite partner by symmetry.
Answer: Electric field at centre = 0 (zero)
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