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A conductor is placed in a uniform external electric field. Dashed lines represent electric field lines and solid lines represent equipotential surfaces. Points A, B, and C are three locations in the field region outside the conductor. Point A is in a region where field lines are widely spaced (weak field), point B is in a region where field lines are densely packed (strong field), and points A and C lie on the same equipotential surface. Which of the following statements is/are correct?
- (A) The electric field strength at point A is less than that at point B.
- (B) The electric potential at point A is higher than that at point B.
- (C) Moving a negative charge from point A to point B involves positive work done by the electric field.
- (D) Moving a negative charge from point A to point C involves zero work done by the electric field.
Correct answer: (A) The electric field strength at point A is less than that at point B.
Solution
Widely spaced field lines at A mean weaker field compared to densely packed lines at B, confirming (A). Points A and C on the same equipotential mean zero work for any charge (D is correct). For (B), the potential ordering depends on direction of field, not determinable without specific figure, but (A) is definitively correct. Statement (C) is incorrect because moving a negative charge from A (lower field region) to B (higher field region, higher potential if field points from B to A) means the electric force on the negative charge is opposite to displacement, giving negative work by the field.
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