[A.] Electrostatic field lines form closed loops.
[B.] The electric field lines point radially outward when charge is greater than zero.
[C.] The Gauss’s Law is valid only for inverse-square force.
[D.] The work done in moving a charged particle in a static electric field around a closed path is zero.
[E.] The motion of a particle under Coulomb’s force must take place in a plane.
Choose the correct answer from the options given below:
A
A, B, C, D Only
B
A, C, E Only
C
B, C, D, E Only
D
A, B, D, E Only
Answer
Correct answer:C
Step-by-step solution
Standard Method
Given: A set of statements about electrostatic field lines, Gauss’s law, work in electrostatic field, and motion under Coulomb force.
Find: Which statements are correct.
Statement-wise analysis:
A. Electrostatic field lines form closed loops. False. Electrostatic field lines originate from positive charges and terminate on negative charges. They do not form closed loops. Closed loops are characteristic of magnetic field lines.
B. The electric field lines point radially outward when charge is greater than zero. True. For a positive point charge, electric field lines emerge radially outward.
C. The Gauss’s Law is valid only for inverse-square force. True. In the standard electrostatic form, Gauss’s law is associated with inverse-square dependence of force.
D. The work done in moving a charged particle in a static electric field around a closed path is zero. True. Electrostatic field is conservative, so
∮E⋅dl=0
and hence the work done over a closed path is zero.
E. The motion of a particle under Coulomb’s force must take place in a plane. True. Coulomb force is a central force, and motion under a central force is confined to a plane.
Therefore, the correct statements are B, C, D, E.
The correct option is C.
Common mistakes
Assuming electrostatic field lines form closed loops because many field diagrams look curved. This is wrong because electrostatic field lines begin on positive charges and end on negative charges. Remember that closed loops are a property of magnetic field lines, not electrostatic field lines.
Confusing a positive charge with a negative charge while deciding field-line direction. This is wrong because field lines point away from positive charge and toward negative charge. First identify the sign of the source charge, then infer the direction.
Forgetting that static electric fields are conservative and concluding non-zero work over a closed path. This is wrong because in electrostatics the line integral over any closed loop is zero. Use the conservative-field property before evaluating work.
Not recognizing Coulomb force as a central force and treating the motion as fully three-dimensional. This is wrong because angular momentum remains fixed in direction for a central force, confining motion to one plane. Use central-force motion principles here.
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