Two protons are kept at a finite distance of 300 nm from each other. What is the nature of the force between them?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Repulsive
Each proton carries the charge \( +e \), so two protons are like charges. By Coulomb’s law, \( F=kq_1q_2/r^{2} \). The separation and the size of the charges decide only how strong the force is. The signs of the charges decide whether it attracts or repels.
Option (1) Attractive — Incorrect. Attraction acts between unlike charges, and both protons are positive.
Option (2) Repulsive — Correct. Like charges repel, so the electrostatic force between the two protons pushes them apart along the line joining them.
Option (3) It depends on the distance of separation — Incorrect. The distance changes the magnitude of the force as \( 1/r^{2} \), but the force between like charges stays repulsive at every distance.
Option (4) It depends on the magnitude of the charges — Incorrect. The magnitudes set the size of the force through the product \( q_1q_2 \). The nature of the force does not change with them.
NCERT (2026-27):
Electric Charge – “… There are two kinds of electrification and we find that (i) like charges repel and (ii) unlike charges attract each other.”