The point of this question is to illustrate how slowly electrons travel on average via a thin wire, even for big values of current.
i) A wire made up from zinc having a cross-section of diameter 0.940 mm carries a current of 12.0 A. Compute the "areal current density"; in another words, determine how many electrons per square meter per second flow via this wire?
ii) The density of zinc is around 7.15 g/cm3, and its atomic mass is 65.3. Supposing each zinc atom contributes two mobile electrons to the metal, determine the number density of free charges in the wire, in electrons/m3?
iii) Employ your outcomes to compute the drift speed (that is, the average total speed) of the electrons in the wire.
iv) Due to the thermal motion, the electrons at room temperature are arbitrarily traveling to and fro at 1.12×105 m/s, even devoid of any current. Determine what fraction is the current's drift speed, as compared to the random thermal motion?