Electric Field and Electric Field Lines

Correct answer: A. Because field is stronger near the charge

Explanation: Electric field-line density is a visual convention for representing field strength. For a point charge, E = k|Q|/r², so the field is stronger at smaller distance r. Lines are therefore drawn closer together near the positive charge and farther apart away from it. They are imaginary representations, not wires, and this spacing is unrelated to gravity or temperature. A is correct.

Correct answer: A. At right angle

Explanation: The governing concept is the electrostatic condition at a conductor’s surface. In electrostatic equilibrium, the electric field inside the conductor is zero, and any tangential component at the surface would move free charges. Therefore, the field just outside must be normal, or perpendicular, to the surface. A perpendicular line makes a 90° angle, so option A is correct. Zero angle would mean the lines run along the surface, while arbitrary angles are not allowed in equilibrium.

Correct answer: A. From positive to negative

Explanation: The governing rule for electrostatic field lines is that their arrows point in the direction of the force on a small positive test charge. Lines originate on positive charges and terminate on negative charges, or extend to infinity if no opposite charge is present. An electric dipole has separated positive and negative charges, so its external field lines run from the positive charge toward the negative charge. Hence option A is correct; the other choices reverse the direction or describe non-electric-field-line patterns.

Correct answer: A. Where more field lines pass through the same area

Explanation: Electric field-line diagrams use line density as a qualitative measure of field magnitude. When the same area is considered, a larger number of lines crossing it represents a greater electric field; closer spacing indicates stronger field intensity. Thus option A is correct. No visible line or widely separated lines indicates a weaker field in the diagram, and erasing lines changes only the drawing, not the physical field. The comparison is meaningful only when the reference area is the same.

Correct answer: A. Uniform field

Explanation: A uniform electric field has constant magnitude and constant direction throughout the considered region. In a field-line diagram, constant direction is represented by parallel lines, while constant magnitude is represented by equal spacing between the lines. Therefore, lines with the same direction and equal separation indicate a uniform field, making option A correct. A non-uniform field generally has changing direction or spacing, and equal spacing does not mean that the field is zero.

Correct answer: A. Electric charge

Explanation: The governing concept is that electric charge produces an electric field in the space around it. A positive charge creates a field directed outward, while a negative charge creates a field directed inward; for several charges, the resultant field is obtained by superposition. Thus electric charge is the fundamental source, so option A is correct. Sound and ordinary heat are not basic sources of an electrostatic field, and a shadow has no physical charge that could generate one.

Correct answer: A. Away from the source charge

Explanation: Coulomb’s law determines both the magnitude and nature of the electrostatic interaction. Charges with the same sign repel, so a positive test charge placed near a positive source charge experiences a force directed away from the source. Therefore option A is correct. The exact geometrical direction depends on the line joining the charges, so it is not necessarily to the right. Attraction and zero force would be incorrect for two isolated positive charges at finite separation.

Correct answer: A. Towards the source charge

Explanation: The direction of an electric field is defined as the direction of force on a positive test charge. A negative source charge attracts a positive test charge, so the force points along the line joining the test charge to the negative source and is directed toward that source. Hence option A is correct. Repulsion would apply to like signs, while “always upward” ignores the actual geometry and “always zero” contradicts the nonzero Coulomb force at finite separation.

Correct answer: A. To represent the direction and strength of the field

Explanation: Electric field lines are an imaginary graphical tool used to visualize an electric field. The arrow at each point indicates the direction of the force on a positive test charge, and the relative density of lines represents the field’s strength: closer lines indicate a stronger field. Therefore option A is correct. Field lines do not measure mass or time and have no relation to the colour of a charge. They are a representation, not material objects.

Correct answer: A. The diagram is incorrect

Explanation: The governing property is that the electric field has a unique direction at every point in space. The tangent to a field line gives that direction. If two electric field lines intersected, their tangents at the intersection would imply two different field directions at one point, which is physically impossible for a single-valued electric field. Therefore option A is correct. Intersection does not indicate uniformity or a zero field; it indicates an invalid field-line drawing.

Correct answer: A. Because the electric field is stronger there

Explanation: For a point charge, the electric-field magnitude is given by E = k|q|/r², so it increases sharply as the distance r from the charge decreases. Field-line diagrams represent this greater magnitude by drawing the lines closer together, or with greater line density, near the charge. Thus option A is correct. The spacing is not caused by light, air, or charge colour; it is a visual convention that communicates the inverse-square variation of field strength.

Correct answer: A. Space around a charge

Explanation: The governing concept is that an electric charge produces an electric field in the space surrounding it. The field at a point represents the force that a unit positive test charge would experience there. Thus another charge placed in that region can be pushed or pulled. Therefore option A is correct; the field is not restricted to the inside of the charge, Earth’s centre, or a sound source.

Correct answer: A. So that the original field is not disturbed

Explanation: The governing idea is that electric field must describe the source charges, not the disturbance produced by the measuring charge. A large test charge could exert an appreciable force on the source charges and alter their arrangement or field. A sufficiently small positive test charge produces negligible disturbance, so the measured force per unit charge represents the original field. Hence option A is correct.

Correct answer: A. In the direction of the electric field

Explanation: An electric field line is an imaginary curve whose tangent at any point gives the direction of the electric field there. Its arrow also indicates the direction in which a positive test charge would be pushed. Therefore moving forward along the indicated field line means moving in the field direction, so option A is correct. The motion is not necessarily opposite, perpendicular, or random.

Correct answer: A. They do not intersect each other

Explanation: A field line is drawn so that its tangent gives the unique electric-field direction at every point. If two field lines intersected, the intersection point would have two different field directions, which is physically impossible. Hence field lines do not intersect, making option A correct. They are not always closed circles, their arrows show direction, and electrostatic lines generally begin on positive charges and end on negative charges or at infinity.

Correct answer: A. Non-uniform

Explanation: The governing representation is that the direction of the field is shown by the line orientation, while the relative density or spacing of lines represents field strength. Straight, parallel lines can indicate a constant direction, but changing spacing indicates that the magnitude changes from place to place. Therefore the field is non-uniform, so option A is correct. A uniform field requires both constant direction and constant strength.

Correct answer: A. Force on a positive test charge

Explanation: By convention, the direction of the electric field at a point is the direction of the force exerted on a small positive test charge placed at that point. Mathematically, E = F/q for positive q, so the force and field vectors have the same direction. A negative charge would experience force opposite to E. Therefore option A is correct; mass, temperature, and wire length do not define field direction.

Correct answer: A. Because its effect is symmetric in all directions

Explanation: A point charge has spherical symmetry: no direction around it is physically preferred. The electric field at every point is directed along the line joining the charge to that point. Consequently, field lines radiate outward from a positive point charge and inward toward a negative one, forming straight radial lines. Thus option A is correct; the other statements contradict the nature of the electric field.

Correct answer: A. The correct field direction will be shown wrongly

Explanation: Electric field lines are graphical representations, and their arrows carry physical meaning: they show the direction of the electric field, defined by the force on a positive test charge. Reversing an arrow therefore gives an incorrect direction, even if the line’s shape remains unchanged. Option A is correct. The reversal cannot alter mass, make an imaginary line physical, or force the field magnitude to become zero.

Correct answer: A. Force acting on a charge

Explanation: Electric field at a point is defined as the electric force experienced per unit positive test charge placed at that point: E = F/q. Thus its basic physical meaning is connected with the force acting on a charge. Option A is correct. Force on a mass belongs to mechanics, current describes charge flow through a conductor, and temperature measures thermal state; none of these gives the definition of electric field.

Correct answer: A. Positive test charge

Explanation: By convention, the direction of the electric field at a point is the direction of the force on a small positive test charge placed there. A positive charge experiences force along the field, whereas a negative charge experiences force opposite to it. Therefore option A is correct. A neutron has no net electric charge, and an atomic nucleus may have different charge and is not the standard reference used to define field direction.

Correct answer: A. Away from the charge

Explanation: The governing concept is the definition of electric-field direction: it is the direction in which a small positive test charge would move. A positive point charge repels a positive test charge, so the force, and therefore the field direction, is radially outward at every surrounding point. Hence field lines originate from the positive charge and spread away from it. Option B describes a negative charge, while C and D contradict the usual field-line representation.

Correct answer: A. Toward the charge

Explanation: Electric-field direction is defined by the force on a positive test charge. A negative point charge attracts such a test charge, so the force points toward the charge from every surrounding location. Field lines are therefore drawn radially inward and terminate on the negative charge. Lines pointing outward represent a positive source, not a negative one. Electric field lines are not generally closed circles, so options B, C and D are unsuitable.

Correct answer: A. Because field cannot have two directions at one point

Explanation: The governing concept is that the electric field is a vector field. At any ordinary point, the resultant electric field has one definite magnitude and one definite direction, obtained by vector addition of all source contributions. If two field lines crossed, their tangents at the intersection would indicate two different field directions at the same point, which is impossible. Thus A is correct; the other options give irrelevant or false reasons.

Correct answer: A. Strength of the field

Explanation: The governing diagrammatic convention is that the density, or closeness, of electric field lines represents the magnitude of the electric field. Lines packed closely together indicate a stronger field, whereas widely separated lines indicate a weaker field. This convention helps compare field strength at different locations without calculating the exact value. It does not directly show charge colour, object mass, or merely the number of particles, so A is the only suitable answer.