- #1

MBBphys

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## Homework Statement

A piece of n-type germanium is 2.0mm wide and 0.25 mm thick. At a certain temperature, the number of conduction electrons per cubic metre is 6 x 10

^{20}m

^{-3}. What is the average drift speed of the electrons when a current of 1.5 mA flows? (e=1.6 x 10

^{-19}

## Homework Equations

I=nAve

## The Attempt at a Solution

So I converted all the units to SI base.

1.5/1000 = 6 x 10

^{20}x (0.125/1000)

^{2}x pi x 1.6 x 10

^{-19}x

**v**

v = 318.309...

v=318 metres per second (3sf).

v = 318.309...

v=318 metres per second (3sf)

But the answer booklet gives 31 metres per second. Am I wrong or is it wrong?

Thanks!