Question

When a metal wire has an electric field applied, electric current flows.

a) If we consider the path the electrons take through the wire in response to the electric field, explain why that path is not the shortest distance between the ends of the wire.

b) Adding thermal energy to the wire increases the kinetic energy of the electrons, however, the resistance of the wire increases. Explain this phenomena.

Answer 1

(a) When the electric field is applied to the ends of the wire, electrons move through the wire because the resistance of the wire is less than the resistance of the surrounding air. Resistance is the obstruction to the flow of electrons hence electrons flow through the path having minimum resistance.

(b) As the thermal energy increases, Kinetic energy of electrons as well as that of positive ions also increase. Hence the mean time between collisions of electrons with ions is reduced due to movement of ions also. That is why Resistance of the wire increases.