A student passes different steady currents through a metallic specimen and measures the corresponding internal electric field E for each current density J. The plot of E versus J is a straight line through the origin.
a. (i) Explain, on the basis of basic definitions, why the E–J graph is linear for a metallic conductor at constant temperature.
b. (ii) Show that the numerical value of the slope of this straight line represents the resistivity of the material.
c. (iii) The measured slope is 4.0×10−8VsC−1m. State the physical quantity this value corresponds to and write its SI unit clearly.