Case: Read the passage and answer the following questions

Conductors contain mobile charge carriers. In metallic conductors, these charge carriers are electrons. In a metal, the outer (valence) electrons part away from their atoms and are free to move. These electrons are free within the metal but not free to leave the metal. The free electrons form a kind of ‘gas’; they collide with each other and with the ions and move randomly in different directions. In an external electric field, they drift against the direction of the field. The positive ions are made up of the nuclei and the bound electrons remain held in their fixed positions.

Which of the following is the correct expression for electric field at the surface of a charged conductor?

E = (σ/ε)n

Electric field on the surface of a charged conductor is E = (σ/ε)n

where σ is the surface charge density and n is a unit vector normal to the surface in the outward direction.