Electric Field and Electric Field Lines

Correct answer: A. Negative

Explanation: By convention, electric field lines originate on positive charges and terminate on negative charges. Therefore, lines directed inward toward a charge indicate that the charge is negative. A positive charge would have lines emerging outward. The pattern does not represent a neutral charge, and under the usual field-line convention the sign can be determined directly, making option A correct.

Correct answer: A. It is a positive charge

Explanation: Electric field lines are defined to point in the direction of the force on a positive test charge. They emerge from positive charges, which act as sources, and terminate on negative charges, which act as sinks. Thus outward-directed lines identify a positive charge. A negative charge would attract the lines inward, while neutrality would not produce this source pattern; option D is unrelated to electric-field sign.

Correct answer: A. Upward

Explanation: The electric field direction is defined as the direction of the force on a positive test charge. Equivalently, the relation is F = qE; because q is positive, the force and field vectors have the same direction. Since the observed force is upward, the electric field is upward. The opposite-direction rule applies only to a negative charge.

Correct answer: A. Straight, parallel and equally spaced

Explanation: Between large, oppositely charged parallel plates, the central region is treated as approximately uniform when edge effects are neglected. A uniform electric field has the same magnitude and direction at each point, so it is represented by straight, parallel, equally spaced lines. Option A therefore shows the standard diagram; circular lines and intersecting lines violate the usual electrostatic-field representation.

Correct answer: A. Toward the left

Explanation: An electron has negative charge. The electric force is F = qE, so when q is negative, the force direction is opposite to the electric-field direction. The field points right, therefore the force on the electron points left. Option B would describe a positive charge in the same field, while option D is unjustified because a nonzero field generally produces a nonzero force on an electron.

Correct answer: A. Twelve newtons

Explanation: The electric force on a charge in an electric field is calculated using F = qE. Substituting q = 2 C and E = 6 N/C gives F = 2 × 6 = 12 N. Because the charge is positive, the force is in the same direction as the field, although only its magnitude is asked here. Therefore option A is correct; dividing or using only one given value gives the distractors.

Correct answer: A. Five newtons per coulomb

Explanation: Electric field is defined as force per unit charge, so E = F/q. With F = 15 N and q = 3 C, E = 15/3 = 5 N/C. Therefore option A is correct. The unit follows because newtons are divided by coulombs. Option B uses the force without division, C multiplies the quantities, and D uses only the charge, so none of those gives the field.

Correct answer: A. One ninth

Explanation: For a point charge, the electric-field magnitude is given by E = k|q|/r², so it varies inversely as the square of the distance. If the distance changes from r to 3r, the new field is E' = k|q|/(3r)² = E/9. Therefore, option A is correct. One third would apply to an inverse-distance law, while the other two choices incorrectly suggest an increase.

Correct answer: A. Four times

Explanation: The electric field of a point charge follows E = k|q|/r². When the distance becomes r/2, the new value is E' = k|q|/(r/2)² = k|q|/(r²/4) = 4E. Thus the field becomes four times its original value, so option A is correct. Doubling would follow an inverse-first-power rule, whereas one-half and one-fourth confuse the direction of the change.

Correct answer: A. In the upper part

Explanation: The density of electric field lines is a visual measure of electric-field strength: closer lines represent a larger magnitude, while widely separated lines represent a smaller magnitude. Since the lines are denser in the upper region, the field is stronger there. The statement concerns magnitude, not merely the direction indicated by the line arrows. Therefore, option A is correct; the lower region is weaker, not equal or field-free.

Correct answer: A. When magnitude and direction are same at every point

Explanation: A uniform electric field is a vector field whose magnitude and direction remain constant from point to point. Thus both conditions must hold simultaneously; constant magnitude alone is insufficient if direction changes, and constant direction alone is insufficient if magnitude changes. Field lines in a valid electrostatic representation do not intersect because that would assign two directions at one point. Therefore, option A is the only correct choice.

Correct answer: A. Toward the right

Explanation: The electric field direction is defined as the force direction on a positive test charge. A positive source charge repels a positive test charge, so its field points radially away from the source. At a point directly to the right of the charge, the outward radial direction is rightward. Therefore, option A is correct. Leftward would be the direction toward the source and is associated with a negative source at that location.

Correct answer: A. Toward the left

Explanation: The electric field direction is the force direction on a positive test charge. A negative source charge attracts such a test charge, so its field points radially toward the negative charge. From a point situated to the right of that charge, the direction toward the source is leftward. Hence option A is correct. Rightward would point away from the negative charge, while upward and downward are perpendicular to the line joining the point and charge.

Correct answer: A. Negative charge

Explanation: In the standard electric-field-line convention, lines originate from positive charges and terminate on negative charges, or extend to infinity when an isolated source has no terminating charge. Therefore, a charge on which field lines end is negative. A positive charge is associated with lines beginning there, while neutrality and whether a particle is metallic do not determine this line-ending rule. Thus option A is correct.

Correct answer: A. Positive charge

Explanation: Electric field lines are defined as imaginary lines whose tangent gives the field direction. By convention, they emerge from positive charges and terminate on negative charges or at infinity. Thus, if the lines begin at the charge, the charge is positive, so option A is correct. Option B reverses the convention, while neutral matter does not act as a source of net field lines in this context.

Correct answer: A. Because field strength is the same everywhere

Explanation: Field lines are a visual representation of an electric field, and their density is used to indicate field strength: closer lines represent a stronger field, while wider spacing represents a weaker field. In a uniform electric field, both magnitude and direction remain constant from point to point. Consequently, the lines are drawn parallel and equally spaced, making option A correct.

Correct answer: A. Force doubles and direction remains the same

Explanation: The electric force on a charge in an electric field is given by F = qE. At the same point, E is unchanged, so replacing q by 2q gives F′ = (2q)E = 2F. Because the new charge is still positive, the force has the same direction as the electric field. Hence option A is correct; doubling the charge does not reverse or eliminate the force.

Correct answer: A. Because they are imaginary lines used to represent the field

Explanation: Electric field lines are imaginary graphical constructions, not material objects or tracks. The tangent to a line indicates the direction of force on a positive test charge, and the density of lines gives a qualitative idea of field strength. A real particle follows its actual equation of motion, which can depend on electric and other forces, initial velocity, and constraints. Therefore option A is correct.

Correct answer: A. Understanding direction and strength of an invisible field from diagrams

Explanation: Electric fields cannot be seen directly, so diagrams and field-line patterns provide an important method for interpreting them. The arrow direction indicates the field direction, while the relative density or spacing of lines indicates qualitative strength. This skill helps solve conceptual and diagram-based questions. The other options concern unrelated properties, so option A is the only suitable answer.

Correct answer: A. Radially outward straight lines

Explanation: A positive point charge repels a positive test charge, so the electric field direction at every surrounding point is away from the charge. Because a point charge has spherical symmetry, its field lines are drawn radially outward in all directions, with the charge as their common origin. They are not inward, circular, or restricted to one parallel direction. Therefore option A is correct.

Correct answer: A. Inward towards the charge

Explanation: The direction of an electric field is defined as the direction of force on a positive test charge. A negative point charge attracts such a test charge, so the force and field point toward the negative charge. Consequently, field lines are drawn radially inward and terminate at the negative charge. They do not point outward or form closed circles; hence option A is correct.

Correct answer: A. Newton per coulomb

Explanation: Electric field is defined as force per unit positive test charge: E = F/q. Force is measured in newtons and electric charge is measured in coulombs. Therefore the SI unit is N/C, read as newton per coulomb. It is also equivalent to volt per metre, but that alternative is not listed. C/N is the reciprocal quantity, while N·C and C·m do not match the definition, so option A is correct.

Correct answer: A. It becomes double

Explanation: The electric field due to a point charge is E = k|Q|/r². With the distance r unchanged, k and r² remain constant, so E is directly proportional to the magnitude |Q|. Replacing Q by 2Q gives E' = k(2|Q|)/r² = 2E. Therefore the field doubles. It does not become four times because distance has not changed, and it cannot remain unchanged when the source charge changes; option A is correct.

Correct answer: A. Zero

Explanation: A conductor contains free charges that can move in response to an electric field. During electrostatic equilibrium, these charges redistribute themselves until the net force on them inside the conducting material is zero. Consequently, the electric field throughout the interior of the conductor is zero. A nonzero field would keep driving charge motion, contradicting equilibrium. The field is not necessarily maximum, outward, or inward; hence option A is correct under the stated electrostatic condition.

Correct answer: A. Start from positive and end on negative

Explanation: The direction of an electric field line is defined as the direction in which a positive test charge would be pushed. A positive source charge repels such a test charge, so lines emerge from positive charge; a negative charge attracts it, so lines terminate on negative charge. In an isolated charge diagram, lines may extend to or come from infinity, but they do not generally form closed loops. Therefore option A is correct.