The mean free path of conduction electorns in copper is about `4xx10^(-8)`m. for a copper block, find the electric field which can give, on an average, 1eV energy to a conduction electron.

Explanation

Let the electric field be E. the force on an electron is eE. As the electron moves through a distance d, the work done on it is eEd. This is equal to the energy transferred to the electron As the electron travels an average distance of `4xx10^(-8)`m before a collision, the energy transferred is `eE(4xx10^(-8)m)`. To get 2 eV energy from the electric field,
`eE(4xx10^(-8)m)=1eV` energy from the electric field,
`eE(4xx10^(-8)m)=1eV`
or, `E=2.5xx10^(7) V//m`.