NEET UG - Torque on a dipole in a uniform electric field, electric flux, Gauss law and applications Online Test (MCQ Quiz)

1. What is the SI unit of electric flux?

A) Newton per meter (N/m) B) Volt per meter (V/m) C) Newton meter per Coulomb (Nm/C) D) Volt meter (Vm)

2. A dipole of dipole moment p is placed in a uniform electric field E. What is the torque experienced by the dipole?

A) pE B) p.E C) p x E D) E x p

3. For a dipole placed in a uniform electric field, the torque is maximum when the angle between the dipole moment and the electric field is:

A) 0 degrees B) 30 degrees C) 90 degrees D) 180 degrees

4. Gauss's Law relates the electric flux through a closed surface to:

A) The total charge enclosed by the surface B) The electric field at a point outside the surface C) The potential difference across the surface D) The area of the surface

5. If the net charge enclosed by a Gaussian surface is zero, then the electric flux through the surface is:

A) Zero B) Infinite C) Equal to the charge density D) Dependent on the shape of the surface

6. Electric flux is a measure of:

A) The strength of the electric field B) The total electric charge in a region C) The number of electric field lines passing through a surface D) The electric potential at a point

7. What is the condition for minimum torque on a dipole in a uniform electric field?

A) Dipole moment is perpendicular to the electric field B) Dipole moment is parallel to the electric field C) Dipole moment is anti-parallel to the electric field D) Dipole moment is zero

8. Gauss's Law is a direct consequence of:

A) Coulomb's Law B) Ampere's Law C) Faraday's Law D) Biot-Savart Law

9. Which of the following statements is INCORRECT regarding electric flux?

A) Electric flux is a scalar quantity. B) Electric flux is zero if the electric field is perpendicular to the surface. C) Electric flux can be positive, negative, or zero. D) Electric flux depends on the exact shape of the Gaussian surface, not just the enclosed charge.

10. An electric dipole consists of two equal and opposite charges, +q and -q, separated by a distance 2a. If the dipole moment is p, what is its magnitude?

A) q/2a B) 2aq C) q/(2a) D) q*a

11. If a dipole is placed in a non-uniform electric field, the net force on the dipole is generally:

A) Zero B) Non-zero C) Equal to the torque D) Dependent on the dipole moment only

12. What is the magnitude of the electric field at a distance r from an infinitely long charged wire with linear charge density λ, according to Gauss's Law?

A) λ / (2πε₀r) B) λ / (4πε₀r) C) 2λ / (ε₀r) D) λ / (ε₀r)

13. The orientation of a dipole with minimum potential energy in a uniform electric field is when the dipole moment is:

A) Anti-parallel to the electric field B) Perpendicular to the electric field C) Parallel to the electric field D) At an angle of 45 degrees to the electric field

14. Electric flux is defined as the integral of the electric field over a surface: Φ = ∫ E ⋅ dA. If the electric field is uniform and perpendicular to a flat surface of area A, the flux is:

A) EA B) E/A C) Zero D) E²A

15. Consider a point charge q enclosed within a sphere. If the radius of the sphere is doubled, how does the electric flux through the sphere change?

A) It doubles B) It quadruples C) It remains the same D) It halves

16. What is the net torque on an electric dipole in a uniform electric field when it is in stable equilibrium?

A) Maximum B) Minimum (zero) C) Equal to pE D) Equal to -pE

17. Gauss's Law is particularly useful for calculating the electric field of charge distributions with:

A) Irregular shapes B) High symmetry C) No symmetry D) Varying charge densities

18. The potential energy of an electric dipole of dipole moment p in a uniform electric field E is given by:

A) pE B) p.E C) -p.E D) p x E

19. If an electric field line enters a closed surface, it contributes:

A) Positive flux B) Negative flux C) Zero flux D) Infinite flux

20. What is the electric flux through a closed surface that encloses no net charge?

A) Depends on the surface area B) Depends on the electric field strength C) Zero D) Cannot be determined

21. For a dipole aligned anti-parallel to a uniform electric field, the torque is:

A) Maximum and positive B) Maximum and negative C) Zero D) Minimum

22. Application of Gauss's Law: The electric field inside a uniformly charged spherical shell of radius R is:

A) σ / (2ε₀) B) kQ/R² C) Zero D) σ / ε₀

23. The direction of the dipole moment is from the negative charge to the:

A) Negative charge B) Positive charge C) Center of the dipole D) Electric field

24. If the electric field is parallel to the area vector of a surface, the electric flux is:

A) Zero B) Maximum C) Minimum D) Negative

25. What is the magnitude of the electric field at a distance r from an infinite plane sheet of charge with uniform surface charge density σ, according to Gauss's Law?

A) σ / ε₀ B) σ / (2ε₀) C) 2σ / ε₀ D) σr / ε₀

26. The net flux through a closed surface is zero. This implies that:

A) The electric field is zero everywhere on the surface. B) There are equal amounts of positive and negative charge enclosed. C) There is no charge enclosed by the surface. D) The surface is not a Gaussian surface.

27. A dipole is in unstable equilibrium in a uniform electric field when its dipole moment is:

A) Parallel to the electric field B) Anti-parallel to the electric field C) Perpendicular to the electric field D) At 45 degrees to the electric field

28. Which quantity is conserved in any process involving electric charges, according to Gauss's Law?

A) Electric field strength B) Electric potential C) Net electric flux D) Net charge enclosed

29. The work done in rotating a dipole from an angle θ₁ to θ₂ in a uniform electric field E is given by:

A) pE(cosθ₁ - cosθ₂) B) pE(cosθ₂ - cosθ₁) C) pE(sinθ₂ - sinθ₁) D) pE(sinθ₁ - sinθ₂)

30. If a closed surface is placed in a non-uniform electric field, the net electric flux through the surface is zero if:

A) The field is zero inside the surface. B) The surface is very large. C) The net charge enclosed is zero. D) The field lines are all parallel.

31. The magnitude of the electric field at the surface of a conductor carrying a surface charge density σ is:

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

32. For a dipole aligned perpendicular to a uniform electric field, the torque is:

A) Zero B) Maximum C) Minimum D) Negative

33. Gauss's Law can be used to find the electric field due to a point charge q at a distance r by choosing a Gaussian surface as:

A) A cube centered on the charge B) A plane sheet C) A sphere centered on the charge D) An infinite cylinder

34. When is the potential energy of a dipole in a uniform electric field equal to zero?

A) When the dipole moment is parallel to the field B) When the dipole moment is anti-parallel to the field C) When the dipole moment is perpendicular to the field D) When the electric field is zero

35. The unit of electric flux, Vm, is equivalent to:

A) N m²/C B) N C/m² C) C/m D) J/C

36. If a dipole is in equilibrium in a uniform electric field, the net torque on it is:

A) Maximum B) Minimum C) Zero D) Constant

37. What is the electric flux through a closed surface if it contains an electric dipole?

A) Depends on the dipole's orientation B) Non-zero C) Zero D) Cannot be determined

38. Application of Gauss's Law: The electric field outside an infinitely long charged cylinder with radius R and linear charge density λ at a distance r > R is:

A) λ / (2πε₀r) B) λ / (4πε₀r) C) 2λ / (ε₀r) D) λ / (ε₀r)

39. The dipole moment vector points from the negative charge towards the positive charge. In a uniform electric field, the dipole tends to align itself:

A) Anti-parallel to the field B) Perpendicular to the field C) Parallel to the field D) In a random direction

40. If the electric field lines are diverging from a closed surface, the net flux is:

A) Zero B) Negative C) Positive D) Infinite

41. Gauss's Law is not generally useful for calculating the electric field of:

A) A uniformly charged sphere B) An infinitely long charged wire C) An arbitrarily shaped charged object D) An infinite charged plane

42. The torque on a dipole in a uniform electric field is zero when the dipole moment is:

A) Parallel to the electric field B) Anti-parallel to the electric field C) Perpendicular to the electric field D) Either parallel or anti-parallel to the electric field

43. Electric flux is proportional to the number of electric field lines passing through a surface. If the surface area is doubled while keeping the field constant and perpendicular, the flux:

A) Halves B) Doubles C) Remains the same D) Increases by a factor of four

44. Consider a Gaussian surface enclosing a net charge Q. If another charge q is brought near the surface but outside it, the net flux through the surface:

A) Increases by an amount proportional to q B) Decreases by an amount proportional to q C) Remains unchanged D) Becomes zero

45. The stable equilibrium position of an electric dipole in a uniform electric field is when the angle between the dipole moment and the electric field is:

A) 0 degrees B) 90 degrees C) 180 degrees D) 270 degrees

46. What is the magnitude of the electric field inside a uniformly charged solid conducting sphere?

A) Zero B) Non-zero and uniform C) Varies with distance from the center D) Depends on the charge density only

47. If a dipole moment p is rotated by 180 degrees in a uniform electric field E, the change in potential energy is:

A) Zero B) 2pE C) -2pE D) pE

48. The net electric flux through a closed surface is given by Gauss's Law: Φ = Q_enclosed / ε₀. If the enclosed charge is positive, the flux is:

A) Negative B) Zero C) Positive D) Dependent on ε₀

49. A dipole is in unstable equilibrium if its potential energy is:

A) Minimum B) Maximum C) Zero D) Negative

50. If an electric field is uniform, the net flux through any closed surface entirely within that field, enclosing no charge, is:

A) Non-zero B) Zero C) Infinite D) Dependent on the surface shape

Torque on a dipole in a uniform electric field, electric flux, Gauss law and applications - Online Test

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