Conductors and Insulators

Correct answer: A. Zero

Explanation: The governing concept is electrostatic equilibrium of free charges in a conductor. If a nonzero electric field existed inside, the conductor’s free charges would experience a force F = qE and continue moving, so the situation would not be electrostatic. The charges redistribute themselves until their net internal field becomes zero. Therefore option A is correct. The field is not necessarily negative, infinite, or very high; those choices confuse field value with charge distribution or potential.

Correct answer: A. On the outer surface

Explanation: In electrostatic equilibrium, free charges cannot remain distributed through the conductor’s interior because an internal electric field would make them move. They rearrange until the field inside the conducting material is zero, leaving excess charge on the surface. For a conductor with no internal cavity charge, it resides on the outer surface. Thus A is correct; volume, centre, and cavity-only distributions are not generally valid.

Correct answer: A. Perpendicular to the surface

Explanation: In electrostatic equilibrium, the electric field at a conductor’s surface cannot have a tangential component. If it did, free charges would experience a force along the surface and continue moving, contradicting equilibrium. Therefore, just outside the conductor, the field is normal to the surface; its direction is outward for a positively charged conductor and inward for a negatively charged one. Thus option A is correct, while B describes an impossible equilibrium condition and D applies inside the conductor, not just outside.

Correct answer: A. In electrostatic condition

Explanation: The governing condition is electrostatic equilibrium. In a conductor at equilibrium, free charges are able to move and rearrange until the electric field inside the conducting material becomes zero; otherwise they would continue to experience force and move. This result is not restricted to vacuum, temperature, or a flowing-current state. Therefore option A is correct. A conductor carrying steady current generally has a nonzero internal electric field.

Correct answer: A. Zero

Explanation: For a conductor in electrostatic equilibrium, the electric field everywhere within the conducting material is zero, including a point just inside its surface. If a nonzero field existed there, mobile charges would feel a force and move, contradicting equilibrium. The field just outside may be nonzero and is normal to the surface, but that is a different location. Hence option A is correct; the other choices confuse inside and outside behavior.

Correct answer: A. Surface charge density

Explanation: The relevant conductor result is the boundary condition just outside a charged conductor: E_out = σ/ε₀ in the normal direction, where σ is the local surface charge density. Thus the field becomes larger where charge is more densely concentrated, especially near sharp regions. It is not determined by colour, the name of the material, or mass alone. Therefore option A is correct, with the understanding that the statement refers to electrostatic equilibrium.

Correct answer: A. Zero

Explanation: In electrostatic equilibrium, the free charges inside a conductor have no net motion. If a nonzero electric field existed within the conducting material, it would exert force on these charges and produce a current. The charges therefore redistribute themselves until the internal field becomes zero. This is a fundamental property of conductors in electrostatics, so option A is correct; the other choices are not general results.

Correct answer: A. On the outer surface

Explanation: A conductor contains mobile charges. In electrostatic equilibrium, they move until the electric field inside the conducting material is zero. Gauss’s law then shows that a Gaussian surface wholly within the conductor encloses no net excess charge. Consequently, excess charge is located on the conductor’s surface; for an isolated conductor without an internal cavity charge, it resides on the outer surface. Therefore option A is correct.

Correct answer: A. Perpendicular to the surface

Explanation: At the surface of a conductor in electrostatic equilibrium, the electric field cannot have a tangential component. Such a component would exert a force along the surface and make free charges move, contradicting equilibrium. Hence the field is normal, or perpendicular, to the surface just outside the conductor. Its external magnitude may be nonzero, so option D is incorrect. Therefore option A is correct.

Correct answer: A. Zero

Explanation: The governing concept is electrostatic equilibrium in a conductor. Free charges move until the electric field within the conducting material becomes zero; excess charge remains on the outer surface. Gauss’s law also gives zero enclosed net charge for a Gaussian surface completely inside the conductor, so the electric flux and field are zero. Therefore, option A is correct; the other choices incorrectly predict a nonzero or infinite interior field.

Correct answer: A. Surface charge density

Explanation: The governing boundary condition for a conductor is that the electric field just outside its surface is normal to the surface and has magnitude E = σ/ε₀, where σ is the local surface charge density. Thus, greater charge concentration produces a stronger nearby field, especially near sharp regions. Option A is correct; colour, name, and sound have no role in this electrostatic relation.