Electrostatic Properties of a Conductor

Electrostatics of Conductor Some of the important points to be noted about the electrostatic properties of a conductor are as follows:

Electrostatic field is zero inside a conductor:

In static condition, a conductor neutral or charged, the electric field inside the conductor is zero everywhere. This is one of the defining properties of a conductor. We know that a conductor contains free electrons which, in the presence of an electric field, experience a drift or a force. Inside the conductor, the electrons distribute themselves in such a way that the final electric field at all points inside the conductor is zero.

Electrostatic field lines are normal to the surface at every point in a charged conductor:

We can say that, if the electric field lines were not normal at the surface, a component of the electric field would have been present along the surface of a conductor in static condition. Thus, free charges moving on the surface would also have experienced some force leading to their motion, which does not happen. Since there are no tangential components, the forces have to be normal to the surface.

In static condition, interior of the conductor contains no excess charge:

We know that any neutral conductor contains an equal amount of positive and negative charges, at every point, even in an infinitesimally small element of volume or surface area. From the Gauss’s law we can say that in case of a charged conductor, the excess charges are present only on the surface. Let us consider an arbitrary volume element of the conductor, which we denote as ‘v’ and for the closed surface bounding the volume element, electrostatic field is zero. Thus, the total electric flux through S is zero. So, from the Gauss law, it follows that the net charge enclosed by the surface element is zero. As we go on decreasing the size of the volume and the surface element, at a point we can say that when the element is vanishingly small, it denotes any point in the conductor. So the net charge at any point inside the conductor is always zero and the excess charges reside at the surface.

Constant electrostatic potential throughout the volume of the conductor:

The electrostatic potential at any point throughout the volume of the conductor is always constant and the value of electrostatic potential at the surface is equal to that at any point inside the volume.

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Practise This Question

Four metal conductors having different shapes
1. A sphere
2. Cylindrical
3. Pear
4. Lightning conductor

Which shape will sustain its charge for the longest time?