NEET (UG)

Practice Test 1 — Electrostatics

12 questions • 18 minutes • auto-graded with full solutions

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Section A — MCQ (Single Correct)

Question 1

If the distance between two point charges is doubled, the force becomes:

Solution: $F \propto 1/r^2$; doubling $r$ gives $1/4$.

Question 2

The SI unit of electric field is:

Solution: $E = F/q$, so units are $\text{N C}^{-1}$ (or $\text{V m}^{-1}$).

Question 3

Total electric flux through a closed surface enclosing charge $q$ is:

Solution: Gauss's law: $\Phi = q/\varepsilon_0$.

Question 4

The field of a short dipole on its axis varies as:

Solution: Dipole field $\propto 1/r^3$.

Question 5

Electric potential due to a point charge varies as:

Solution: $V \propto 1/r$.

Question 6

The energy stored in a capacitor of charge $Q$ and capacitance $C$ is:

Solution: $U = Q^2/2C$.

Question 7

Three $6\ \mu\text{F}$ capacitors in series give an equivalent capacitance of:

Solution: $1/C_s = 3/6 = 1/2 \Rightarrow C_s = 2\ \mu\text{F}$.

Question 8

The work done in moving a charge over an equipotential surface is:

Solution: $\Delta V = 0 \Rightarrow W = 0$.

Section B — Assertion & Reason

Question 9

A: The electric field inside a charged hollow conductor is zero.
R: Any excess charge on a conductor resides on its outer surface.

Solution: Charge on the surface and zero internal field are linked — R explains A.

Question 10

A: The electric field is always perpendicular to an equipotential surface.
R: No work is done in moving a charge along an equipotential surface.

Solution: Zero work along the surface means the field has no component along it, i.e. it is perpendicular — R explains A.

Question 11

A: The capacitance of a capacitor increases when a dielectric is inserted.
R: The dielectric reduces the effective field between the plates by becoming polarised.

Solution: Polarisation lowers the field, raising $C = Q/V$ — R explains A.

Question 12

A: The total electric flux through a closed surface changes when an external charge is brought near it.
R: By Gauss's law, flux depends only on the charge enclosed by the surface.

Solution: External charge does not change the net flux, so A is false; R correctly states Gauss's law.