Conductors and Insulators

A positively charged metal sphere has a deficiency of electrons. Earthing provides a conducting path between the sphere and Earth, which acts as a very large reservoir of charge. Electrons therefore move from Earth into the sphere until its potential is equalized with Earth’s potential, reducing or neutralizing the positive charge. Conventional current would be described in the opposite direction, but electron flow is from Earth to the sphere. Hence option A is correct.

A conductor contains mobile electrons. If an electric field existed inside it during electrostatic equilibrium, these free charges would continue to move, so equilibrium would not exist. They redistribute until the internal field is zero and excess charge lies on the outer surface. Thus A is correct; charge is not destroyed, protons do not normally leave, and conductors can certainly be charged.

In a metal, the positive ions and their protons are bound within atomic nuclei, while conduction electrons can move through the material. A conductor becomes positively charged when some of its mobile electrons are removed, leaving an electron deficiency. Thus option B is correct. Protons do not flow out, neutrons do not become charged, and charge is transferred rather than destroyed.

The relevant conductor principle is that metals contain mobile conduction electrons, whereas the positively charged atomic ions occupy nearly fixed lattice sites. When an electric field or contact disturbs charge balance, electrons drift and redistribute rapidly through the material; the heavy ions do not move appreciably. Therefore option A is correct. Protons are bound inside nuclei, neutrons are neutral, and lattice charge does not simply disappear.

For a conductor in electrostatic equilibrium, its free charges rearrange themselves until the net electric field inside the conducting material becomes zero. Otherwise, a nonzero field would exert force on free charges and cause continuous motion. Hence the field inside is zero, not maximum, upward, or continually changing. Therefore, option A is correct.

In electrostatic equilibrium, the electric field has no tangential component at a conductor’s surface. If a tangential component existed, free charges would move along the surface until that component vanished. Consequently, the field just outside the conductor is normal, or perpendicular, to the surface; its magnitude may be σ/ε₀ for a suitable surface charge density. Thus A is correct.

A conductor contains mobile charges. In electrostatic equilibrium these charges redistribute themselves until the net electric field inside the conducting material becomes zero. If a nonzero field remained, it would exert force on free charges and produce current, contradicting equilibrium. This result applies to the interior of the conductor, not necessarily to the external field. Hence option A is correct.

The governing concept is electrostatic equilibrium in a conductor. Free charges can move through the conductor, so any tangential component of the electric field at the surface would exert a force and cause charges to move. In equilibrium that tangential component must be zero; the remaining electric field is perpendicular, or normal, to the conductor’s surface. Hence option A is correct. Options B and C imply tangential motion, while D ignores the boundary condition.

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.

The governing electrostatic principle is that the electric field inside a conductor in electrostatic equilibrium is zero. Conduction electrons are free to move, so any internal electric field would exert force on them and produce a current. They redistribute themselves, usually on the surface, until their induced field cancels the interior field. Thus A is correct; charge can exist on the surface, while B, C, and D are physically false.

In electrostatic equilibrium, the electric field at a conductor’s surface must be normal to the surface. If field lines meet it obliquely, they have a tangential component. That component would exert a force on mobile surface charges and make them move, contradicting electrostatic equilibrium. Thus the shown diagram cannot represent the stated condition, so A is correct. The other choices incorrectly claim universal validity, a large interior field, or absence of surface charge.

In electrostatic equilibrium, free charges inside a conductor have stopped moving. If the electric field had a tangential component along the conductor’s surface, it would exert a force on these mobile charges and make them move. Charges redistribute until the tangential component becomes zero, leaving only the normal component. Therefore field lines meet the surface normally. Option A gives the governing reason; the other statements are false or irrelevant.

The governing concept is electrostatic equilibrium in a conductor. Conductors contain mobile charges, and any internal electric field would exert force on them, causing motion. The charges therefore redistribute themselves, mainly on the surface, until their induced field cancels the internal field. Hence the net electric field inside is zero. Options B, C, and D are false because conductors can contain charge, obey force laws, and are not defined as magnetic materials.

In electrostatic equilibrium, free charges inside a conductor must experience no force along its surface. An oblique electric field has a tangential component, E_t, parallel to the surface. The force qE_t would drive mobile charges along the conductor, causing redistribution until the tangential component becomes zero. Consequently, the remaining field at the surface is normal. The other options describe no electrostatic consequence.

The governing concept is electrostatic charge distribution on a conductor. In equilibrium, excess charge resides on the outer surface and concentrates more strongly where the surface is sharply curved. A pointed region can therefore have greater surface charge density, producing a stronger nearby electric field; field-line density represents field strength. The point is not necessarily negative, the material remains a conductor, and field lines never intersect.

The governing electrostatic-conductor rule is that the electric field inside a conductor in equilibrium is zero; otherwise free charges would move. For a positively charged spherical conductor, symmetry makes the external field radial and directed outward, equivalent to the field of a point charge at the centre outside the sphere. Thus A is correct. The other choices incorrectly assign a field inside, deny the external field, or violate the properties of electrostatic field lines.

In electrostatic equilibrium, free charges in a conductor must have zero net force. A tangential electric-field component would exert a force qE_parallel along the surface, causing mobile charges to drift. Their redistribution would continue until that component disappeared. Hence the field at the surface can have only a normal component, making option A correct. Conductors do contain free charges, and their surfaces need not be spherical.

A conductor contains mobile free charges. If a nonzero electric field persisted inside it, these charges would experience force and continue moving, contradicting electrostatic equilibrium. They redistribute on the conductor’s surface until their field cancels the internal field, giving zero net field inside. Therefore option A is correct. The conductor still has atoms, does not become an insulator, and distance remains physically meaningful.

The governing electrostatic-conductor principle is that the electric field inside a conductor is zero in equilibrium because free charges redistribute until the internal force vanishes. This does not mean the surface charge disappears. Excess charge remains on the outer surface and produces an electric field in the exterior region. Thus option A is correct. Option B contradicts equilibrium, while C and D incorrectly deny the conductor’s influence and surface charge.

In electrostatic equilibrium, free charges inside a conductor must have no continuing motion. If the electric field had a tangential component along the surface, a free charge would experience a force qE_t and would accelerate or drift along that surface. Charges redistribute until the tangential component becomes zero; only the normal component may remain just outside. Therefore A is correct. B is wrong because conductors do contain mobile charges, while C and D misunderstand electric-field properties.