King Edward Medical University Entry Test Physics: Electrostatics MCQs

King Edward Medical University Entry Test Physics: Electrostatics MCQs — sample questions

1. Question 1

   Q1. The unit of electric field intensity in SI system is

   • A) N/C
   • B) V/m
   • C) J/C
   • D) C/N

   Answer: N/C

   Explanation: Electric field intensity is measured in N/C; V/m is equivalent but not the primary unit. C/N is incorrect.

2. Question 2

   Q2. Coulomb's law is applicable to

   • A) Point charges
   • B) Large spheres
   • C) Charged plates
   • D) Current carrying wires

   Answer: Point charges

   Explanation: Coulomb's law applies to point charges; it can be extended to larger objects with certain assumptions.

3. Question 3

   Q3. The electric potential at a point due to a point charge is given by

   • A) kQ/r
   • B) kQ/r^2
   • C) kQr
   • D) kQ/r^3

   Answer: kQ/r

   Explanation: Electric potential due to a point charge is kQ/r; kQ/r^2 is the electric field, not potential.

4. Question 4

   Q4. The capacitance of a capacitor depends upon

   • A) Charge on plates
   • B) Potential difference between plates
   • C) Geometry of capacitor
   • D) Dielectric material

   Answer: Geometry of capacitor

   Explanation: Capacitance depends on geometry; charge and potential difference are related but not the primary factors.

5. Question 5

   Q5. A capacitor is charged by a battery. The battery is removed and a dielectric slab is inserted. What happens to the charge?

   • A) Increases
   • B) Decreases
   • C) Remains the same
   • D) Becomes zero

   Answer: Remains the same

   Explanation: Charge remains the same as battery is removed; dielectric affects capacitance and potential difference.

6. Question 6

   Q6. The electric flux through a closed surface is proportional to

   • A) Charge enclosed
   • B) Charge outside
   • C) Surface area
   • D) Electric field

   Answer: Charge enclosed

   Explanation: Gauss's law states that flux is proportional to enclosed charge; outside charge doesn't affect total flux.

7. Question 7

   Q7. Two charges q1 and q2 are placed at a distance r. If the force between them is F, what happens to F if r is doubled?

   • A) F/2
   • B) F/4
   • C) 4F
   • D) 2F

   Answer: F/4

   Explanation: Coulomb's law states F ∝ 1/r^2; doubling r reduces F to F/4.

8. Question 8

   Q8. The SI unit of capacitance is

   • A) Farad
   • B) Henry
   • C) Ohm
   • D) Tesla

   Answer: Farad

   Explanation: Farad is the unit of capacitance; Henry is for inductance, Ohm for resistance, Tesla for magnetic field.

9. Question 9

   Q9. When a dielectric is inserted between the plates of a capacitor, its capacitance

   • A) Increases
   • B) Decreases
   • C) Remains the same
   • D) Becomes zero

   Answer: Increases

   Explanation: Dielectric increases capacitance by reducing electric field between plates.

10. Question 10

    Q10. The electric field due to a uniformly charged infinite plane sheet is

    • A) σ/2ε₀
    • B) σ/ε₀
    • C) σ/(2ε₀ + σ)
    • D) Zero

    Answer: σ/2ε₀

    Explanation: Electric field due to infinite plane sheet is σ/2ε₀; doesn't depend on distance.

11. Question 11

    Q11. A charge is placed at the center of a spherical Gaussian surface. The electric flux through the surface is

    • A) q/ε₀
    • B) q/(4πε₀)
    • C) 4πε₀q
    • D) q/(4πε₀r^2)

    Answer: q/ε₀

    Explanation: Gauss's law states that flux is q/ε₀; depends on enclosed charge, not surface details.

12. Question 12

    Q12. The potential difference between two points in an electric field is

    • A) Work done per unit charge
    • B) Force per unit charge
    • C) Energy per unit charge
    • D) Both A and C

    Answer: Both A and C

    Explanation: Potential difference is work done per unit charge, equivalent to energy per unit charge.

13. Question 13

    Q13. The electric field inside a conductor is

    • A) Zero
    • B) Maximum
    • C) Minimum
    • D) Variable

    Answer: Zero

    Explanation: Inside a conductor, electric field is zero in electrostatic equilibrium.

14. Question 14

    Q14. The charge on a capacitor is given by

    • A) CV
    • B) C/V
    • C) QV
    • D) V/C

    Answer: CV

    Explanation: Charge on a capacitor is given by Q = CV; relates capacitance, charge, and potential difference.

15. Question 15

    Q15. A capacitor is connected to a battery. A dielectric slab is inserted. What happens to the potential difference?

    • A) Increases
    • B) Decreases
    • C) Remains the same
    • D) Becomes zero

    Answer: Remains the same

    Explanation: Potential difference remains the same as battery maintains it; dielectric affects capacitance.

16. Question 16

    Q16. The electric potential due to a dipole at a point on its axis is

    • A) k2p/r^3
    • B) k2p/r^2
    • C) kp/r^2
    • D) kp/r^3

    Answer: k2p/r^3

    Explanation: Potential due to dipole on its axis is k2p/r^3; depends on dipole moment and distance.

17. Question 17

    Q17. The force between two charges is F. If a third charge is introduced between them, the force between the original two charges

    • A) Increases
    • B) Decreases
    • C) Remains the same
    • D) Becomes zero

    Answer: Remains the same

    Explanation: Introducing a third charge doesn't affect the force between the original two; superposition principle applies.

18. Question 18

    Q18. The surface charge density on a conductor is

    • A) Proportional to electric field
    • B) Inversely proportional to electric field
    • C) Equal to electric field
    • D) Unrelated to electric field

    Answer: Proportional to electric field

    Explanation: Surface charge density is proportional to electric field just outside; related through ε₀.

19. Question 19

    Q19. The energy density in an electric field is given by

    • A) 1/2 ε₀E^2
    • B) 1/2 ε₀E
    • C) ε₀E^2
    • D) ε₀E

    Answer: 1/2 ε₀E^2

    Explanation: Energy density in electric field is 1/2 ε₀E^2; relates energy stored to field strength.

20. Question 20

    Q20. A point charge of 2 μC is placed 0.5 m away from another point charge of -3 μC. What is the magnitude of the electrostatic force between them?

    • A) 0.216 N
    • B) 0.108 N
    • C) 0.054 N
    • D) 0.027 N

    Answer: 0.216 N

    Explanation: Coulomb's Law gives F = k * q1 * q2 / r^2 = 0.216 N. Wrong options are due to incorrect unit conversions.