Two rods of copper and iron with the same cross-sectional area are joined at S and a steady current I flows through the rods as shown in the figure. Choose the most appropriate representation of charges accumulated near the junction S .

Step-by-step solution

When a current flows through a junction or a contact between two metals of different conductivities a charge is accumulated in the vicinity of contact. The charge accumulation is directly proportional to the current. Charge accumulation occurs in a region whose thickness is nearly equals to the mean free path in the metal. In case current flows from a metal of large conductivity to a metal of small conductivity, charge accumulation is of positive type and vise-versa.