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diamter of a wire isaacphyics

this question is on the diameter of a germanium wire it gives me the free electron density which is 10^28 the current which is 2 A the drift velocity 0.20m/s and that's it I used the formula I=vAnq to get the area of the 2/(0.2*1.6*10^-19*10^20) and it gives me 0.625 then knowing that the area of a circle is pir2 I did 0.625/pi and square rooted the answer to give the radius which I then doubled to get the diameter of 0.89206 I have tried it to 2 and 1 sig-fig but isaacphysics says I'm wrong and I cant find my mistake

Reply 1

Joinedup

I think you just need to check your unit conversion

worth noting that the low electron density of semiconductors like Germanium compared to metals means you can get surprisingly high drift velocities with the same parameters that give modest drift velocities in a metal... and of course you need surprisingy large areas in order to get a modest drift velocity.