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# Mean Drift Velocity watch

1. The mean drift velocity Vx of electrons in X is 2.0 x 10-5ms-1.
Use the fact that X has twice the cross-sectional area of the thinner wire Y to calculate the mean drift velocity Vy of electrons in Y. Show your working.

So I used the equation I = Anev, rearranged for V = I/Ane. Because the current and the number of electrons and the charge will be the same I cancelled those out, to get v = 1/A. I said that v ∝ 1/1/2A = v ∝ 2/A. I know i'm supposed to multiple the mean drift velocity of X by 2 to get Y but i'm not sure why, by looking at the equation.
2. I would do approach it differently.

I = nAev and since n and e can't change, I α Av

This makes it simpler, to me at least. If Y has twice the area of X; then it must have double the drift vel in order to keep the current the same.
3. (Original post by phys981)
I would do approach it differently.

I = nAev and since n and e can't change, I α Av

This makes it simpler, to me at least. If Y has twice the area of X; then it must have double the drift vel in order to keep the current the same.
Yeah thank you, that makes a lot more sense and is more simple as well.

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