What is Drift speed: Definition and 36 Discussions

In physics a drift velocity is the average velocity attained by charged particles, such as electrons, in a material due to an electric field. In general, an electron in a conductor will propagate randomly at the Fermi velocity, resulting in an average velocity of zero. Applying an electric field adds to this random motion a small net flow in one direction; this is the drift.
Drift velocity is proportional to current. In a resistive material it is also proportional to the magnitude of an external electric field. Thus Ohm's law can be explained in terms of drift velocity. The law's most elementary expression is:

u
=
μ
E
,

{\displaystyle u=\mu E,}
where u is drift velocity, μ is the material's electron mobility, and E is the electric field. In the MKS system these quantities' units are m/s, m2/(V·s), and V/m, respectively.
When a potential difference is applied across a conductor, free electrons gain velocity in the direction opposite to the electric field between successive collisions (and lose velocity when traveling in the direction of the field), thus acquiring a velocity component in that direction in addition to its random thermal velocity. As a result, there is a definite small drift velocity of electrons, which is superimposed on the random motion of free electrons. Due to this drift velocity, there is a net flow of electrons opposite to the direction of the field.

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1. Find the drift speed of electrons in a wire

We need to find each variable. ##I## is already given to us as 8 amps. The charge of an electron is 1.6 x 10^-19 coulombs. The cross sectional area will just be ##\pi(1.2∗10^−3)^2## m^2. Now we need to find the free electron density. We are given the density of of copper and can use dimensional...
2. Find the drift speed of of the electrons

I've found I to be .167 using the potential and resistance. I also found the volume by multiplying the cross-sectional area by the length (?) and then dividing the # of conducting electrons into that to find packing density (n). To find drift speed, I would also need the area of the block as...
3. How to calculate the current in a 400 nm wire of graphene

Hi, I need to calculate the current in a 400nm piece of graphene. Can some one help me please? I found online that graphene has electron mobility of 200,000 cm^2/( V s). My best attempt is as follows. Using the equation vd = uE where E is the magnitude of the electric field applied to a...
4. A

What is the relationship between displacement, speed, and time in a random walk?

http://imgur.com/a/hFubT http://imgur.com/a/fquuF In the first image, first line in the last paragraph. The first sentence define that carriers move with an average velocity component Vd in the x direction(in fact, carriers also move with an average velocity component in the y...
5. Finding the drift speed of a conduction electrons

Homework Statement The figure shows wire section 1 of diameter 4R and wire section 2 of diameter 2R, connected by a tapered section. The wire is copper and carries a current. Assume that the current is uniformly distributed across any cross-sectional area through the wire's width. The electric...
6. Find Electron Current Through Iron Wire

Homework Statement What electron current is driven through a 1.4-mm-diameter iron wire by a 0.070 V/m electric field? The mean time between collisions in iron is 5.2×10^−15s . A=1.5*10^-6 m^2 ne=8.5*10^28 m^-3 Homework Equations I know I need to use ie = neAVd, but I'm having trouble finding...
7. Finding the electron drift speed

Homework Statement A piece of n-type germanium is 2.0mm wide and 0.25 mm thick. At a certain temperature, the number of conduction electrons per cubic metre is 6 x 1020 m-3. What is the average drift speed of the electrons when a current of 1.5 mA flows? (e=1.6 x 10-19 Homework Equations...
8. How can an increase in area cause a decrease in drift speed?

Homework Statement We have: I=nAve Imagine a copper wire with a constant current through it: I=constant e=constant n (for copper)=constant Hence, we obtain: A is inversely proportional to electron drift velocity. My question is: how does that make sense? Why would the cross sectional area...
9. Drift Speed of Electrons in Conductor with Applied Field

for an electron, randomly moving inside a conductor , having applied an external electric field we have those electrons moving with a net speed called drift speed , against the direction of field. so initially as electrons are moving randomly we consider their initial velocity o and after time t...
10. Exploring the Drift Speed of Electrons in Conductors

Homework Statement :[/B] When a steady current flows through a conductor, the electrons in it move with a certain average 'drift speed'. The drift speed of electrons for a typical copper wire is about 1 mm s-1 . How is it then that an electric bulb lights up as soon as we turn the switch on...
11. What limits the speed of a computer or cell phone?

I am just beginning to educate myself about electricity and computers. Every time I read something I realize my ignorance is even greater than I imagined. For instance, I was stunned to learn that the drift speed of a typical current is so slow. An AC circuit generates an electromagnetic field...
12. What is the drift speed for plasma?

Homework Statement I need to calculate the drift speed, drift orbital period and current density for 1eV protons and 10eV electrons. The density is 5 cm^-3 The assumption is that it is only a grad-B drift Homework Equations <V> = [6*E/(qBo*L*Re)](0,35 + 0.15sin(a)) The Attempt at a Solution...
13. Drift speed of an electron in normal atmospheric conditions

Homework Statement How fast would a electric arc be when it ionizes through normal, unpressured air between say, two electrodes? Not the same as lightning as it is hypothetically from an artificial source. Homework Equations How would one calculate (please include your formula's and which...
14. Derivation of drift speed question

Homework Statement First off, this is NOT a homework problem. This is a conceptual question I have regarding the derivation of the drift velocity v_d =[(qE)/m] \tau Typically, when this formula is derived, you first calculate the acceleration of a particle in the electric field (qE/m) and...
15. Why Does Electron Drift Speed Remain Constant Despite Continuous Electric Field?

So in Resnick & Halliday, it explains that the drift speed, or the average speed of charge moving in a wire under the influence of an electric field E is defined by the equation ## J = (ne)v_{d} ##. Now if J,n,e are all constants then the drift speed ##v_{d}## will also be a constant. But this...
16. Electron drift speed, Current, and Electric field in hollow wire?

Homework Statement A hollow copper wire with an inner diameter of 1.4 mm and an outer diameter of 2.6 mm carries a current of 2.50 amps. Copper has an electron density of 8.5x1028 m-3 and a conductivity of 6.0x107 (ohm m)-1. a. What is the electron drift speed in the wire? b. What is the...
17. Electron drift speed in metals

Is there a physical explanation for why electrons move through a metal with a relatively low drift speed? Or is it just the observed phenomenon? I find it hard to visualise electrons moving relatively slowly through a metal despite the current flowing through it being quick...can anyone help? Thx
18. Ion Drift Speed Help Much Needed!

Help much needed! Thanks!So this problem has been dealt with here on the physics forums. But the fact is that answers either appear to be false and/or they differ from what other people have done. First, here's the problem: In a certain region, the atmospheric electric field strength is 120...
19. What are (a) the current density and (b) the electron drift speed?

Homework Statement "The current in a 1.70mm x 1.70mm square aluminum wire is 1.70 A. What are (a) the current density [in MA/m^2] and (b) the electron drift speed [in micrometers/second]?" Homework Equations J = I/A The Attempt at a Solution I plugged in the values for current...
20. Current Density and Electron Drift Speed

Homework Statement The current in a 1.5 mm X 1.5 mm square aluminum wire is 1.10 A. What are (a) the current density and (b) the electron drift speed? Homework Equations current density: J = I/A drift speed Vd = J/ne The Attempt at a Solution It's asking for an answer in MA/m^2...
21. Drift Speed of the Conduction Electrons

Homework Statement An aluminum wire with a diameter of 0.100 mm has a uniform electric field of 0.200 V/m imposed along its entire length. The temperature of the wire is 50.0 C. a) Determine resistivity b) Current density c) Total current d) Drift speed of the conduction electrons...
22. Amatuer question about electron drift speed.

I'm teaching myself some physics, and I am having some difficulty with the concept of drift speed. My book derived the time between collisions using ma=Eq and then substituting the acceleration into the first equation of kinematics and solving for v(final) as the drift speed. The time it...
23. Find Drift Speed of Electrons in Copper Wire | Tom

Homework Statement I’m trying to find the drift speed of electrons in a copper wire. The length of the wire is 10 meters, temp is 60°C, current is 5 A and the total resistance of the wire is 0.05 ohms. Homework Equations # of charge carriers (n) = density * 6.02 x 10^23/molar mass...
24. Why Does qEt/m Represent Drift Speed in a Conductor?

Homework Statement v=qEt/m t=time between each collision q=charge on particle m=mass of particle E=electric field Why is this the average velocity/drift speed in a conductor? Homework Equations The Attempt at a Solution Doesn't qEt/m = the final velocity of the...
25. Drift speed of electrons and holes in semiconductors

I would request for help in understanding why the drift speed of electrons in semiconductors is more than that of holes. Thanks.
26. Simple drift speed probem driving me nuts

Homework Statement A current of 200 mA flows in a silver wire of radius 0.8mm. Find (a) the drift speed of the electrons. (b) the number density of particles. Homework Equations The Attempt at a Solution The answer in the book is 1.07 x 10^-5, but I'm getting 1.06 x 10^-4. Can anyone tell me...
27. Relating Current Density and Drift Speed

Homework Statement The figure shows wire section 1 of diameter 4R and wire section 2 of diameter 2R, connected by a tapered section. The wire is copper and carries a current. Assume that the current is uniformly distributed across any cross-sectional area through the wire's width. The electric...
28. Finding electron drift speed

Homework Statement 1.0 * 10^20 electrons flow through a cross section of a 2.0-mm-diameter iron wire in 5.0 s. What is the electron drift speed? Homework Equations v_d = e*tao/m * E i_e = n_e * e * tao * A/m * E The Attempt at a Solution I can't seem to get very far. I think...
29. What is the drift speed of Na+ ions while the current flows?

Homework Statement A. When current flows in an ionic solution, both negative and positive ions are charge carriers. In the dilute limit, the resistivity of the solution is inversely proportional to the concentration. For example, the resistivity of salt water solution at 25 °C is ρ =...
30. Drift speed and current density

Homework Statement A piece of copper wire joins a piece of aluminum wire whose diameter is five times that of the copper. The same current flows in both wires. The density of conduction electrons in copper is 1.1 \times 1029 m-3 in aluminum it is 2.1\times1029 m-3. what is the drift speed...
31. How long does it take an electron to travel 150 km on a copper cable?

Homework Statement A 150 km long high-voltage transmission line 2.0 cm in diameter carries a steady current of 1030 A. If the conductor is copper with a free charge density of 8.9 1028 electrons per cubic meter, how many years does it take one electron to travel the full length of the cable...
32. Determining current and drift speed

[SOLVED] Determining current and drift speed Homework Statement http://img162.imageshack.us/img162/145/problemrg5.jpg The two wires in the above figure are made of the same material. What are the current and the electron drift speed in the 2.0mm-diameter segment of the wire. Homework...
33. What is the unique drift speed for a charged particle in crossed E and B fields?

Homework Statement I am working on a problem and don't know if I am going about it right because I am stuck. A charged particle of mass m and positive charge q moves in uniform electric and magnetic fields, E pointing in the y direction and B in the z direction (an arrangement called "crossed...
34. Electron drift speed in a copper wire.

I'm really stuck on this one problem: "A small but measurable current of 4.20E-10 A exists in a copper wire whose diameter is 0.02 cm. Calculate the electron drift speed (in meters/second)." Source: Serway and Jewett I know that: I = 4.20E-10 A n = 8960 kg/m^3 q = 1.6E-19 C d = 2E-4...
35. How Long Does an Electron Take to Travel the Length of a High-Voltage Cable?

Homework Statement A 200-km-long high-voltage transmission line 2 cm in diameter carries a steady current of 1000 A. If the conductor is copper with a free charge density of 8.5 x 10^28 electrons per cubic meter, how many years does it take one electron to travel th full length of the cable...
36. Electron Drift Speed: Find Current Density &amp; Current in a Gold Wire

The electron drift speed in a gold wire is 3.0 * 10^-4. 1. What is the current density in the wire? 2. What is the current if the wire diameter is 0.50 mm? J = I / A and I = nqva What is the answer?