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wat is the direction of drift velocity with reference to the applied electric field?

wat is the direction of drift velocity with reference to the applied electric field?

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2 Answers

SAGAR SINGH - IIT DELHI
878 Points
13 years ago

Dear student,

I = \frac{\Delta Q}{\Delta t}
where
ΔQ is the small amount of charge that passes through an area in a small unit of time, Δt.

One can relate ΔQ to the motion of charged particles in a wire expecting a dependence on the number density of the charge carriers and using dimensional analysis.

ΔQ = \left( \mathrm{number \ of \ charged \ particles} \right) \times \left( \mathrm{charge \ per \ particle} \right)

= \left( n A \Delta x \right) q
where
n is the number of charge carriers per unit volume
A is the area
Δx is a small length along the wire
q is the charge of the charge carriers

Now, normally particles move randomly, but under the influence of an electric field in the wire, the charge carriers gain an average velocity in a specific direction. This is what's called drift velocity, vd. And since Δx = vd Δt, we can plug it into the above equation.

\Delta Q = \left( n A v_d \Delta t \right) q

Putting that back into the original equation and re-arranging to solve for the drift velocity:

v_d = \frac{I}{n q A}

mathew jacob
16 Points
13 years ago

the drift velocity has opposite dir as that of electric field because electrons experience force in that dir ie opp to electric field

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