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BoanviaFx
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Homework Statement
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Can someone confirm if I answered correctly? Thanks
Ai) Define the term drift velocity with reference to a current in a circuit.
ii) Derive an expression to describe the current passing through a metallic conductor of cross-sectional area A having n charge carriers per unit volume.
Bi) Two cylindrical conductors of the same material are connected together as shown in figure(
Current passes through the first conductor which has a cross-sectional radius r1 and an associated drift velocity of v1. The second conductor has a cross-sectional radius of r2. Express the drift velocity, v2, of the electrons in second material in terms of the other quantities.
ii) The conductors are made of iron which has 1028 charge per unit volume. The conductors carry a current of 1A. Given that the radii of the first and second cylinders are given by 0.5mm and 3.0mm respectively, determine the drift velocity within each conductor.
Homework Equations
The Attempt at a Solution
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Ai) The drift velocity is the velocity of the electrons moving across a conductor, and colliding with nearby particles. This is when a p.d is applied and the electrons move from a lower potential to a higher potential thus creating an electric current.
ii) Solution:
I=Q/t Formula for Current.
Q=nAle Formula for Charge.
v = l/t Formula for drift velocity.
t = l/v
Substituting:
I = (nAle)/(l/v)
I = nAve New Expression
Bi) Since Current is the same in both conductors:
I1=I2
n1A1v1e1=n2A2v2e2
so A1v1=A2v2
Therefore v2 = A1v1/A2
Area would be substituted with πr2
ii)
A1 = 7.85x10-7
A2 = 2.82x10-5
e = 1.6x10-19
Conductor 1 Drift velocity
v = I/nAe
v = 1/(1028*7.85x10-7*1.6x10-19)
v = 7.96x10-4
Conductor 2 Drift velocity
v = I/nAe
v = 1/(1028*2.82x10-5*1.6x10-19)
v = 2.21x10-5