Electrostatics of Conductors

The relevant property is electrostatic shielding. In a closed conducting enclosure, mobile charges redistribute on its surfaces until the conductor reaches electrostatic equilibrium. The field produced by this induced surface distribution opposes the applied external field within the enclosure; for an ideal closed conductor with no internal charge, the net field inside is zero. Therefore A is correct, while the other options describe unrelated phenomena.

The surface-charge rule applies specifically to electrostatic equilibrium. Free charges in a conductor move under electric forces until the field inside the conducting material becomes zero. If excess charge remained in the interior, it would create an electric field and drive further motion, contradicting equilibrium. Consequently, excess charge resides on the surface, with its density possibly varying over the surface. The other listed states do not define this electrostatic condition, so A is correct.

Earthing is governed by potential equalisation. Earth is a huge charge reservoir whose potential is conventionally taken as zero, or as a fixed reference. When a conductor is connected to Earth, electrons can flow between them until the conductor reaches the earth’s potential, subject to the surrounding electric conditions. Thus option A is correct. Earthing does not make potential infinite, depend on colour, or transform potential into mass.

Earthing connects the conductor to Earth, a very large charge reservoir whose potential is conventionally taken as zero reference. Charge can flow between the conductor and Earth until the conductor reaches the same potential as Earth, provided the connection is effective and equilibrium is reached. Therefore option B is correct. Earthing does not make potential infinite, relate it to colour, or transform potential into mass; those alternatives contradict electrostatic principles.

The governing concept is equipotential behavior in electrostatics. Earthing provides a conducting connection between the conductor and Earth, which is treated as a very large charge reservoir with a fixed reference potential, conventionally zero volts. Charge can flow until the conductor and Earth reach the same potential, although nearby charges may still produce surface-charge redistribution. Therefore option B is correct. The potential is not necessarily positive, negative, or infinite; its value is tied to Earth’s potential.

When two conductors are connected, electrostatic equilibrium requires equal electric potential, not generally equal charge. For identical conducting spheres, equal potential implies equal charge, but for conductors with different sizes or capacitances, Q = CV means their charges can differ even though their potentials are equal. Hence option A is correct. The other situations do not contradict equal sharing when the bodies are identical or the wording is otherwise incomplete.