isaac physics

I have to find out the diameter of a wire from I=vAnq so ihave the drift velocity of 0.2 m/s the current of 2 amps the free electron density of germanium is 10^28 so ive done 2/(0.2*1.6*10^-19*10^20) which give me 0.625 then did that over pi and square rooted it to get the radius then doubled it to get diameter I got 0.89206.... ive doen it to 1 and 2 sigfig but it keeps saying I'm wrong can someone please point out where I have gone wrong

Reply 1

JaredzzC

You've used two separate values for the number density of charge carriers in your post, although I assume one of them is a mistake because using

n=1 \times 10^{28}

produces an extremely small number, which is not realistic.

We know that

I = nAve \Rightarrow A=\dfrac{I}{nve}

Plugging in the values you mentioned then I get

A = 0.625

, which is the same as you so everything is right so far.

A = \pi r^2 [br]\Rightarrow \pi r^2 = 0.625[br]\Rightarrow r = 0.446[br]\Rightarrow 2r = 0.892 = d

Your calculations arre correct, so it's just a case of your units and any significant figures.

Your least accurate data value is given to 1 significant figure, so your answer should be to 1 significant figure.
0.892 to 1sf is 0.9, have you tried that?

Isaac physics is always very specific with accuracy values and measurements.

If that doesn't work then it's best to check your units.
Are you sure everything is in terms of amps, m, s, etc.... i.e in base units?