Electric Field and Electric Field Lines

Correct answer: A. Field may be treated as approximately uniform

Explanation: The geometry of field lines gives two kinds of information. Nearly straight lines indicate that the field direction changes very little across the selected region, while nearly equal spacing indicates that the field magnitude is almost constant there. Combining both observations justifies treating the field as approximately uniform over that small area. Thus option A is correct. Equal spacing does not mean zero field, and the diagram alone cannot establish that only a negative charge produces it.

Correct answer: A. Where the lines are closer

Explanation: In a field-line diagram, the density of lines represents the relative magnitude of the electric field: closer lines indicate a stronger field, while wider spacing indicates a weaker field. The force on a charge is F = qE. Because the charge is the same and positive at both locations, the larger E produces the larger force. Therefore option A is correct. Option B reverses the density rule, C incorrectly claims zero force, and D ignores the role of field magnitude.

Correct answer: A. Because field decreases inversely with square of distance

Explanation: For an isolated point charge, the electric-field magnitude is E = k|Q|/r². The source charge Q and Coulomb constant k remain fixed, so increasing the distance r makes the denominator r² larger and reduces the field rapidly. Consequently, the field is strongest close to the charge and weaker farther away. Option A states this inverse-square dependence. The charge does not change sign with distance, distance clearly matters, and the field exists at both near and far points, so B, C, and D are incorrect.

Correct answer: A. Direction shows field direction and density shows field strength

Explanation: An electric-field-line diagram encodes two separate physical properties. The arrow direction gives the direction of the electric field, equivalently the force direction on a positive test charge. The relative density or closeness of lines indicates the field magnitude: denser lines mean a stronger field. Therefore both features are needed to interpret the diagram completely, so option A is correct. The other choices assign nonphysical meanings such as colour, time, or charge age.

Correct answer: A. Zero

Explanation: Use the superposition principle: the net electric field is the vector sum of the fields produced by both charges. At the midpoint, equal positive charges are at equal distances, so they produce equal field magnitudes. The field from the left charge points right, and the field from the right charge points left. These equal opposite vectors cancel, giving a net field of zero. Hence A is correct.

Correct answer: A. From positive charge to negative charge

Explanation: Electric field lines emerge from a positive charge and terminate on a negative charge. At the midpoint, the field due to the positive charge points away from the positive charge, toward the negative charge. The field due to the negative charge points toward that negative charge, in the same direction. Their equal magnitudes therefore add, so the net field is from positive to negative. Thus A is correct, not zero.

Correct answer: A. Two directions would exist at one point

Explanation: At every point in space, the electric field vector has one definite direction, provided the field is defined there. The tangent to a field line represents that direction. If two field lines intersected, their tangents at the intersection would indicate two different field directions at the same point, which is impossible. Thus A explains the error; intersection does not imply weak field, changing charge, or physically real lines.

Correct answer: A. Direction is the same but strength is increasing

Explanation: Electric field-line direction represents the direction of the electric field, while line density represents its relative magnitude. Straight, parallel lines show that the direction remains the same. Because the lines become closer together, their density increases and the field strength increases in that direction. A uniform field would require parallel lines with constant spacing, so option B is not correct; the field is neither necessarily zero nor reversing.

Correct answer: A. The net electric field there is zero

Explanation: The governing relation is F = qE, where F is the electric force, q is the test charge, and E is the net electric field. Since q is small but positive and the measured force is zero, E must be zero at that point. This means the vector sum of all source fields vanishes; individual source fields may still be present. Therefore B is incomplete, while C and D contradict the conditions.

Correct answer: A. The field decreases as distance increases

Explanation: The governing idea is that the density of electric field lines represents the relative strength of the field. For an isolated point charge, the magnitude follows E = k|q|/r², so it decreases as distance r increases. Consequently, lines are drawn closer near the charge and farther apart away from it. The pattern does not indicate increasing or constant strength, and field magnitude is not determined only by direction.

Correct answer: A. Zero

Explanation: Let the equal charges be separated symmetrically, with midpoint P between them. Each negative charge produces a field of equal magnitude at P, and each field points toward its own charge. These two field vectors are opposite in direction, so by superposition E_net = E − E = 0. The individual fields are not absent; they cancel exactly. Therefore options B, C, and D are incorrect.

Correct answer: A. From positive charge to negative charge

Explanation: Electric field lines are defined to point in the direction of force on a positive test charge. They originate at a positive charge and terminate at a negative charge. Therefore, in the outer region of an electric dipole, the arrows are drawn from the positive charge toward the negative charge. Option B reverses the conventional direction, while C and D do not describe the complete dipole pattern.

Correct answer: A. So that it does not disturb the original field

Explanation: Electric field at a point is defined using a sufficiently small positive test charge, with E = F/q. The charge must be small so that its own electric field does not significantly redistribute the source charges or alter the field being measured. Thus option A is correct. Its sign, mass, or the closure of field lines is unrelated to this requirement.

Correct answer: A. Upward

Explanation: The force on a charge is given by F = qE. For a negative charge, q is less than zero, so the force vector points opposite to the electric-field vector. The force here is downward; reversing its direction gives an upward electric field. Therefore option A is correct. Option B would be correct for a positive charge, not for a negative one.

Correct answer: A. Electrostatic field goes from positive to negative

Explanation: Electrostatic field lines have a definite beginning and end: they emerge from positive charges and terminate on negative charges, or extend to infinity when no opposite charge is present. Hence they do not form closed loops. This also reflects the conservative nature of an electrostatic field. Option A expresses the relevant idea; B, C, and D are scientifically incorrect.

Correct answer: A. Equal magnitude toward the right

Explanation: Equally spaced, parallel field lines represent a uniform electric field: both its direction and magnitude remain constant in the shown region. Since the arrows point from left to right, a positive test charge experiences force to the right, using F = qE. The force magnitude is also constant for the same charge. Thus A is correct; B reverses direction and D incorrectly assumes zero field.

Correct answer: A. Its magnitude is larger

Explanation: Electric field-line diagrams use the number or density of lines to represent the relative strength of the electric field and, for isolated charges drawn at comparable distances, the magnitude of charge. More lines therefore indicate a larger |q| and stronger electric influence. They do not provide information about mass or temperature, and a neutral object is not represented by a greater set of lines. Hence option A is correct.

Correct answer: A. By drawing a tangent at that point

Explanation: By definition, the electric-field direction at a point is the direction of the tangent to the field line at that point, with the arrow indicating the positive direction. For a curved line, the entire curve does not give one single local direction; the tangent does. The centre of curvature is not generally the field direction, and colour or arbitrary choice has no physical meaning. Hence option A is correct.

Correct answer: A. Yes, they may cancel each other

Explanation: The principle of superposition states that the net electric field is the vector sum of the fields produced by all charges: E_net = E₁ + E₂ + …. Individual fields can therefore be nonzero while equal and opposite contributions cancel at a particular point, giving E_net = 0. This does not mean that no charges exist or that the field is magnetic. Thus option A is correct.

Correct answer: A. Closer to the smaller charge

Explanation: Step 1: Between like charges, fields can be opposite at points on the joining line. Step 2: The larger charge produces a stronger field, so balance occurs closer to the smaller charge. Step 3: For unequal like charges, the zero point is not at the midpoint.

Correct answer: A. Because both fields point in the same direction between them

Explanation: Between a positive and a negative charge, the field due to the positive charge points away from the positive charge, while the field due to the negative charge points toward the negative charge. In the region between them, these directions are the same, so the fields add rather than cancel. Therefore option A is correct; unequal magnitude is not needed for this directional conclusion.

Correct answer: A. The field direction is changing with position

Explanation: The tangent to an electric field line at any point gives the local direction of the electric field. If a line is strongly curved, its tangent direction changes significantly as position changes; this indicates a spatially varying field direction and commonly a non-uniform field. Curvature does not mean the field is zero, nor does it mean lines intersect. Therefore option A is correct.

Correct answer: A. Multiply for magnitude and reverse the direction

Explanation: For a charge q in an electric field E, the force is F = qE. Its magnitude is |F| = |q|E, so the magnitude must use the absolute value of the charge, not a negative numerical direction. Since q is negative, the force direction is opposite to the upward field, namely downward. Thus option A correctly combines multiplication for magnitude with direction reversal.

Correct answer: A. Direction of force on a positive test charge

Explanation: Step 1: The direction of electric field is defined as the direction of force on a positive test charge. Step 2: A negative charge would feel force in the opposite direction, but that does not define the field direction. Step 3: In exams, imagine a tiny positive test charge at the point.

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

Explanation: The governing concept is that the electric field vector at any particular point has one definite direction, given by the force on a positive test charge. A field line is drawn tangent to this direction. If two field lines crossed, their common point would require two different field directions simultaneously, which is impossible. Therefore, intersection is not allowed; the other options describe incorrect properties of electric fields.