electric current, current density and ohms law

Revision |Electric Current|Current Density|Ohm's Law

The electric intesity E, current density j and conductivity sigma are related as:

The electric field E, current density j and conductivity sigma of a conductor are related as

The expression for Ohm's law in terms of electric field E and current density J is:-

Introduction OF Electric Current || Current Density || Current in a Conductor

Electric current is passing through a solid conductor PQ from P to Q. The electric current densities at p and Q are in the ratio.

Answer the following questions : (a) A steady current flows in a metallic conductor of non-uniform cross-section. Explain which of these quantities is constant along the conductor : current, current density, electric field and drift speed ? (b) Is Ohm's law universally applicable for all conducting elements ? If not, give examples of elements which do not obey Ohm's law. (c) A low voltage supply from which one needs high currents must have low internal resistance, why ? (d) A high tension (HT) supply of say 6 kV must have a very large internal resistance. why ?

Introduction |Electric Current|Current Density|Questions