Electric field and field lines - Question Bank

1. The electric field lines are always directed from regions of higher electric potential to regions of lower electric potential. This means:
A) Electric field is parallel to equipotential lines.
B) Electric field is perpendicular to equipotential lines.
C) Electric field is zero where potential is highest.
D) Electric field is strongest where potential is constant.
2. What is the electric field at the surface of a charged conductor if it is placed in a dielectric medium of relative permittivity εr?
A) σ / ε₀
B) σ / (ε₀εr)
C) σε₀εr
D) σε₀ / εr
3. Electric field lines map out the direction and magnitude of the electric field. Which statement is true?
A) The density of lines represents the direction of the field.
B) The number of lines originating from a positive charge is proportional to the magnitude of the charge.
C) Field lines can start or end at any arbitrary point.
D) Field lines represent the path of electrons.
4. The electric field strength at a distance r from a point charge Q is proportional to:
A) 1/r
B) 1/r²
C) r
D) r²
5. Which of the following correctly describes the electric field lines from a system of one positive and one negative charge of equal magnitude?
A) They start from the positive charge and end on the negative charge, forming curved paths.
B) They are parallel lines moving from positive to negative.
C) They are concentric circles around the positive charge.
D) They diverge outwards from both charges.
6. The electric field lines are closer together where the electric field is:
A) Weak
B) Strong
C) Uniform
D) Zero
7. What is the unit of electric flux?
A) Newton per meter squared (N/m²)
B) Volt-meter (V·m)
C) Newton-meter squared per Coulomb (Nm²/C)
D) Coulomb per meter squared (C/m²)
8. Electric field lines are perpendicular to the surface of a conductor because:
A) The electric field inside a conductor is zero
B) Charges reside on the surface of a conductor
C) There is no electric field parallel to the surface of a conductor in equilibrium
D) The conductor is an insulator
9. If the electric field lines are diverging from a point, it indicates the presence of a:
A) Negative charge
B) Positive charge
C) Neutral point
D) Charged conductor
10. What is the electric field at the center of a uniformly charged solid sphere?
A) Zero
B) Maximum
C) Non-zero and finite
D) Infinite
11. The electric field strength is proportional to the:
A) Number of field lines
B) Density of field lines
C) Spacing between field lines
D) Area enclosed by field lines
12. In the case of an electric dipole, the electric field lines are:
A) Straight lines radiating outwards
B) Closed loops
C) Curved lines starting from the positive charge and ending on the negative charge
D) Parallel lines
13. Electric field lines can never cross each other because:
A) Charges would repel
B) The electric field at a point must have a unique direction
C) The net charge would be zero
D) The medium prevents crossing
14. What is the electric field at the surface of a charged conductor in vacuum?
A) Zero
B) σ / (2ε₀)
C) σ / ε₀
D) 2σ / ε₀
15. If the electric field is E, and a small area element is dA, the electric flux through this element is given by:
A) E * dA
B) E / dA
C) E . dA
D) E + dA
16. The electric field lines for a system of two identical negative charges:
A) Converge to a point between the charges
B) Diverge from a point between the charges
C) Repel each other
D) Show neutral points at infinity
17. What is the electric field at the center of a uniformly charged ring?
A) Maximum
B) Non-zero and directed along the axis
C) Zero
D) Infinite
18. Consider a point charge q. The electric field lines are denser closer to the charge. This illustrates that the electric field strength:
A) Is constant everywhere
B) Decreases with distance from the charge
C) Increases with distance from the charge
D) Is zero at the charge
19. Electric field lines are drawn to be perpendicular to the equipotential surfaces. This implies:
A) Electric field is parallel to equipotential surfaces.
B) Work done in moving a charge along an equipotential surface is zero.
C) Electric field is zero on equipotential surfaces.
D) Electric potential is zero on equipotential surfaces.
20. The electric field strength is given by E = F/q. Here, q is:
A) The source charge creating the field
B) A positive test charge
C) A negative test charge
D) Any arbitrary charge
21. Which of the following statements about electric field lines is true?
A) They represent the path of a positive test charge.
B) They indicate the direction of the force on a positive test charge.
C) They are always closed loops.
D) Their density is inversely proportional to the electric field strength.
22. In a region of uniform electric field, electric field lines are:
A) Converging
B) Diverging
C) Parallel and equally spaced
D) Curved
23. Electric field lines are used to visualize:
A) Electric potential
B) Electric current
C) Electric field
D) Electric charge
24. What is the electric field at the surface of a charged conductor?
A) Zero
B) Maximum
C) σ/ε₀, where σ is the surface charge density
D) σ*ε₀
25. For a uniformly charged sphere, the electric field outside the sphere behaves as if the charge were concentrated at:
A) The center of the sphere
B) The surface of the sphere
C) A point at infinity
D) Any point on the surface
26. The electric field is conservative. This means that the work done by the electric field in moving a charge between two points is:
A) Infinite
B) Zero
C) Dependent on the path taken
D) Equal to the potential difference
27. Which of the following represents the electric field of a dipole?
A) Radial lines originating from a single point
B) Parallel lines
C) A pattern of curved lines originating from the positive charge and terminating on the negative charge
D) Concentric circles
28. What happens to the electric field lines when they enter a conducting medium?
A) They become denser
B) They stop abruptly
C) They terminate on the surface of the conductor
D) They pass through the conductor
29. If two charges +q and -q are placed at a distance d apart, the electric field at the midpoint of the line joining them is:
A) Zero
B) Maximum
C) Minimum but non-zero
D) Directed towards the negative charge
30. Electric field lines are drawn such that the number of lines per unit area perpendicular to the lines is proportional to:
A) The potential difference
B) The charge density
C) The electric field strength
D) The permittivity of the medium
31. What is the electric field at a distance r from an infinitely long uniformly charged wire with linear charge density λ?
A) Proportional to 1/r
B) Proportional to 1/r²
C) Proportional to r
D) Constant
32. Consider a large sheet of charge with uniform surface charge density σ. The electric field lines near the sheet are:
A) Curved
B) Parallel and perpendicular to the sheet
C) Diverging from the sheet
D) Converging towards the sheet
33. If the number of electric field lines passing through a surface is N, and the surface area is A, what is the approximate electric field strength if the lines are perpendicular to the surface?
A) N / A
B) A / N
C) N * A
D) N + A
34. What is the net electric flux through a closed surface enclosing a net charge Q?
A) Q / ε₀
B) Q * ε₀
C) Zero
D) Dependent on the shape of the surface
35. Which of the following statements about electric field lines is incorrect?
A) They are continuous curves.
B) They start from positive charges and end on negative charges.
C) They can form closed loops.
D) The tangent to a field line at any point gives the direction of the electric field at that point.
36. The electric field lines due to a system of two equal and opposite charges (a dipole) are:
A) Straight lines
B) Closed loops
C) Elliptical or curved lines starting from positive and ending on negative
D) Parallel lines
37. The electric field lines due to a system of two identical positive charges are:
A) Converging at infinity
B) Diverging from a point between the charges
C) Repelling each other
D) Showing a neutral point at infinity
38. What is the electric field inside a hollow charged conductor?
A) Maximum at the center
B) Non-zero but constant
C) Zero
D) Equal to the field outside
39. Electric field lines are perpendicular to the surface of a conductor in electrostatic equilibrium.
A) Always true
B) True only for charged conductors
C) True only for conductors in a uniform external field
D) Never true
40. Electric field lines are parallel and equally spaced in the field of:
A) A point charge
B) An electric dipole
C) An infinite line charge
D) A uniformly charged infinite plane
41. What is the electric field at the center of an electric dipole?
A) Maximum
B) Zero
C) Non-zero but finite
D) Infinite
42. For a negative point charge, electric field lines are directed:
A) Radially outwards
B) Tangentially
C) Along the axis of symmetry
D) Radially inwards
43. For a positive point charge, electric field lines are directed:
A) Radially inwards
B) Radially outwards
C) Tangentially
D) Along the axis of symmetry
44. What is the electric field at an infinite distance from a point charge?
A) Infinite
B) Finite and non-zero
C) Zero
D) Undetermined
45. Can electric field lines intersect each other?
A) Yes, they can intersect at any point
B) Yes, but only if the charges are of opposite sign
C) No, electric field lines never intersect
D) Yes, they can intersect if there is a neutral point
46. What does the density of electric field lines represent?
A) The direction of the electric field
B) The magnitude of the electric field
C) The polarity of the charge
D) The total charge enclosed
47. Which property of electric field lines indicates the direction of the electric field at a point?
A) Density of lines
B) Number of lines
C) Direction of the tangent to the line
D) Spacing between lines
48. Electric field lines terminate on which type of charge?
A) Positive charge
B) Neutral charge
C) Negative charge
D) Induced charge
49. Electric field lines originate from which type of charge?
A) Negative charge
B) Positive charge
C) Neutral charge
D) Both positive and negative charges
50. What is the unit of electric field strength?
A) Newton per Coulomb (N/C)
B) Volt per meter (V/m)
C) Ampere per meter (A/m)
D) Joule per Coulomb (J/C)
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