Magnitude of electric field due to a point charge +Q experienced by a test charge q at a distance r from the point charge +Q is equal to:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Magnitude of electric force experienced by the test charge/q
The electric field at a point is the force per unit charge on a test charge placed there.
\( \displaystyle E = \frac{F}{q} = \frac{1}{4\pi\varepsilon_0}\,\frac{Q}{r^{2}} \)
where \( F \) is the force on the test charge \( q \) due to \( +Q \).
Option (1) Magnitude of dielectric force experienced by the point charge/Q — Incorrect. The field of \( +Q \) is found from the force on the test charge, divided by \( q \), not by the source charge \( Q \).
Option (2) Magnitude of electric force experienced by the test charge/q — Correct. This is the definition \( E = F/q \).
Option (3) Magnitude of repulsive force between the point charge and the test charge — Incorrect. A force is not a field; it must be divided by the test charge, and the force need not be repulsive.
Option (4) Magnitude of electric force experienced by point charge Q multiplied by the magnitude of charge on the test charge — Incorrect. A force multiplied by a charge does not have the unit of electric field (N/C); the force must be divided by \( q \).
NCERT (2026-27):
Summary – “… 8. The electric field E at a point due to a charge configuration is the force on a small positive test charge q placed at the point divided by the magnitude of the charge.”