查看完整版本 : drift velocity

fx5509 2013-7-12 07:30 PM

drift velocity

[img]http://i1023.photobucket.com/albums/af354/fx5509/phy_zpsf09794b2.jpg[/img]
用I=nAvQ黎計
v=I/nAq
v=(10/5)/(1*10^28)(1/100^3)(1.6*10^-19)
v=1.25*10^-3 m/s
但係ans係B:smile_41: :smile_41:
請問要點計?
thx!!!!

↗亢龍無悔↙ 2013-7-21 02:37 PM

Total number of conductive electrons = n . A . L
n = number of electrons per unit volume, A = area, L = length
Total charges, Q = n . A . L . q
q = charge carried by one electron
I = Q / t
I = current, Q = total charges, t = time
=> I = ( n . A . L . q ) / t
V = I . R
V = voltage, R = resistance
=> V / R = ( n . A . L . q ) / t
v = L / t
v = drift velocity, L = length, t = time
=> L and t are eliminated. => V / R = n . A . v . q
So, I get the same answer with you~
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查看完整版本: drift velocity