Given below are two statements:
Statement I: Two point charges \( +2\,\mu\mathrm{C} \) and \( +8\,\mu\mathrm{C} \) are held a fixed distance apart. The force on the \( +8\,\mu\mathrm{C} \) charge is four times the force on the \( +2\,\mu\mathrm{C} \) charge.
Statement II: The electrostatic force between two point charges acts along the line joining the two charges.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Statement I is false but Statement II is true.
Statement I Two point charges \( +2\,\mu\mathrm{C} \) and \( +8\,\mu\mathrm{C} \) are held a fixed distance apart. The force on the \( +8\,\mu\mathrm{C} \) charge is four times the force on the \( +2\,\mu\mathrm{C} \) charge. — False. By Coulomb’s law the force between the two charges has a single magnitude, \( k\,(2\,\mu\mathrm{C})(8\,\mu\mathrm{C})/r^{2} \). It depends on the product of the charges. The forces of each charge on the other are equal in magnitude and opposite in direction, \( \vec{F}_{12}=-\vec{F}_{21} \), as Newton’s third law requires. The larger charge does not feel a larger force.
Statement II The electrostatic force between two point charges acts along the line joining the two charges. — True. The Coulomb force is directed along the line through the two point charges. Here both charges are positive, so each is pushed directly away from 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.”
Coulomb’s Law – “The force F12 on charge q1 due to charge q2, is obtained … by simply interchanging 1 and 2, i.e.,”
\( \displaystyle \vec{F}_{12}=\frac{1}{4\pi\varepsilon_0}\,\frac{q_1q_2}{r_{12}^{2}}\,\hat{r}_{12}=-\vec{F}_{21} \)
“Thus, Coulomb’s law agrees with the Newton’s third law.”