3. Wire with two different conductivities A wire is made from two different metals with conductivities 01, 02. The two segments have the same radius B. When a current of magnitude I passes to the right through the wire, a thin layer of positive charge appears at the boundary between the two metals, as shown. The segments have lengths L1 and L2, respectively. Surface charge density (a) Use Gauss's law to nd the surface charge density 3 (to avoid confusion with conductivity!) of the thin layer of positive charge at the boundary. (b) In which material is the electric eld larger? How can you tell? (Note that the surface charge density at the boundary is positive as shown in the diagram.) (c) What is the resistance of the entire wire