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 ?