Physics · Electric Charges And Fields · NEET
No. Force acts only when a charge is actually placed there. The electric field exists at a point even when no charge is there yet. Force depends on the charge you place (F = qE), but the field E depends only on the source charge and the distance. In short: the source charge creates the field; the field then decides how much force any charge will feel.
So the answer describes the point in space, not the charge we used to test it. If you place 2q instead of q, the force doubles, but F/q stays the same. Dividing by the test charge removes the size of the test charge and leaves a pure property of that location. That is why E = F/q is the clean definition.
No. A single source charge already sets up a field in all the space around it. We only bring a small test charge to detect or measure the field. The field is there whether or not we check it, just like a hill has a slope even if no ball is rolling down.
The field direction is the direction of force on a positive test charge. So E points away from a positive source charge and toward a negative source charge. A negative charge placed in the field feels a force opposite to E.
A real test charge also pushes on the source charge and can move it, changing the field you are trying to measure. To avoid this, we imagine the test charge as tiny (q to 0) so it disturbs nothing. NCERT states the field is the force on a unit test charge placed 'without disturbing the original positions of charges'.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Newton per coulomb (N/C). It can also be written as volt per metre (V/m); both are equal.
It is a vector. It has both magnitude and direction — the direction of force on a positive test charge. When many charges are present, add their fields as vectors (superposition).
By definition E = F/q. For a single point charge the value is E = kQ/r^2, where k = 9 x 10^9 N m^2/C^2. That point-charge formula is covered on the next page.
Electric field is force per unit charge (a vector, unit N/C). Electric potential is energy per unit charge (a scalar, unit volt). Field tells you the push; potential tells you the stored energy per charge.
It links Coulomb's law, dipoles, flux and Gauss's law. Many NEET questions give a field and ask for force using F = qE, or give a charge setup and ask for the field. Understanding E = F/q is the base for the whole chapter.
