Two point charges, one positive and one negative, are separated by a finite distance. What can you say about the electrostatic force between them?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → The force acts along the line joining the two charges.
Option (1) The force is repulsive. — Incorrect. Repulsion acts between like charges. A positive and a negative charge are unlike charges, and they attract each other.
Option (2) No force acts between them. — Incorrect. Two charges at a finite distance \( r \) always exert a force of magnitude \( k|q_1q_2|/r^{2} \) on each other. This force is not zero for non-zero charges.
Option (3) The force acts along the line joining the two charges. — Correct. By Coulomb’s law, the force between two point charges acts along the line joining them. Here it is attractive, so each charge is pulled towards the other along that line.
NCERT (2026-27):
Coulomb’s Law – “… Coulomb measured the force between two point charges and found that it varied inversely as the square of the distance between the charges and was directly proportional to the product of the magnitude of the two charges and acted along the line joining the two charges.”