Mean Free Path of Electrons

Electricity and Magnetism Level 3

In some metal, the mean free time between interactions of the conduction electrons with the metal is $\tau = 4 \times 10^{-13} \text{ s}$ and the drift velocity of the electrons is $v = 5 \times 10^{-2} \text{ cm}/\text{s}$ . What is the mean free path of the conduction electrons, in meters?

2 \times 10^{-16}

2 \times 10^{-14}

8 \times 10^{-14}

2 \times 10^{-12}

1 solution

Matt DeCross
May 10, 2016

The mean free path is related to the drift velocity and mean free time by the simple equation:

$\lambda = v\tau.$

Plugging in and changing units, one finds:

$\lambda = 5 \times 10^{-2} \text{ cm}/\text{s} \times 4 \times 10^{-13} \text{ s} = 20 \times 10^{-15} \text{ cm} = 2 \times 10^{-16} \text{ m}.$

Mean Free Path of Electrons

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