# What is Mobility: Definition and 47 Discussions

Economic mobility is the ability of an individual, family or some other group to improve (or lower) their economic status—usually measured in income. Economic mobility is often measured by movement between income quintiles. Economic mobility may be considered a type of social mobility, which is often measured in change in income.

View More On Wikipedia.org
1. ### Engineering Mobility of the Mechanism, Chebychev–Grüblerv Formula

For question J) I've got 9 number of links, 10 number of joints and 1 higher pair ( assuming that there is a slippage), substituting these values in the Chebychev–Grübler's formula gives me the mobility of 1. For question H) I've got 7 number of links, 9 number of joints substituting these...
2. ### B Mobility in a Strong Gravity Environment vs. Moving Mass?

This is a basic conundrum that has bothered me for years: if you or a species like you is "adapted" to Twice Gravity (or any other multiple of 9.8m/2 squared) and your life functions and capacities are near identical, How strong/fast are you? Compared to 1G? See, this is the issue of mass vs...
3. ### A Diffussion-limited aggregation and the mobility of particles

How a high mobility of particles over surface cause to aggregation, the professor in the class said that "high mobility causes to local equilibration and thus to a compact aggregation".. which I didn't understand..! What does he mean about local equilibration and how all connect to each other?!
4. ### I Mobility and resistivity as a function of temperature

Referencing: http://www.vlsiinterviewquestions.org/2012/07/21/inverted-temperature-dependence/ Mobility decreases in a MOSFET with increasing temperature However, referencing: https://www.quora.com/Why-does-resistivity-of-semiconductors-decrease-with-increase-in-temperature Resistivity...
5. ### Help me with some of my projects please (wheelchairs and mobility)

Engineers Students Doctors ... i would like to discuss some ideas in my projects .. and also can you tell me how do I know what clients need and want? the first project is about a wheelchair i just added on it a rod when you push it it will create a circular motion to the wheel so he needs...
6. ### Why is there a voltage drop in a metal with no electric field present?

Metals are highly effective at screening electric fields. If we place two contacts reasonably far away from each other on a piece of metal and apply a voltage bias, the charge carriers in the section that is far enough from both the contacts should be unaffected by the electric field. Why then...
7. ### Hall effect -- calculate carrier mobility and density

Homework Statement A metallic film has length L=10mm, width W=1mm and thickness t=1##\mu m##. The current is parallel to the long edge and has magnitude ##I=0.7A##. Longitudinal voltage is ##V=1V## and it doesn't change with magnetic field. The Hall (transverse) voltage ##V_H## increases at...
8. ### Find drift velocity of the current carriers in the copper strip

Homework Statement ABCD is a plane rectangular strip of conducting material of uniform thickness, with a steady current flowing uniformly from AD to BC. The potential difference between E and F, the mid-points respectively of AB and CD, is zero, but when a magnetic field is set up at right...
9. ### How to confirm unit of electron mobility as m^2/(V*S)?

Hello. Electron mobility in plasma is μ = q/m⋅ν, where q, m and ν are charge and mass of electron and electron collisional frequency. (https://en.wikipedia.org/wiki/Electrical_mobility) And unit of the mobility is m2/V⋅S (https://en.wikipedia.org/wiki/Electron_mobility) According to the...
10. ### I Finding mobility constant in the context of the Hall effect

A slab made of unknown material is connected to a power supply as shown in the figure. There is a uniform magnetic field of 0.7 tesla pointing upward throughout this region (perpendicular to the horizontal slab). Two voltmeters are connected to the slab and read steady voltages as shown...
11. ### I Velocity saturation and mobility in metals and semiconductor

Hi, Lately, I've been trying to compare and understand conduction properties of metals and semiconductors. However, there are two question on my mind that I'm still trying to figure out. Maybe someone here might be able to provide some clues. 1. It is known that a linear increase of the...
12. ### Measuring minority carrier density and mobility

Homework Statement Hi all, I'm currently working on a Hall effect lab in which I analyze a p-type sample of germanium (I know it's p-type because I observe a hall voltage inversion point around 350 K which can only happen for a p-type sample). From the Hall and resistivity data I can obtain...
13. ### Discovering the Mobility of the Pictured Mechanism: Analysis and Insights

I need to find the mobility of the pictured system I have labeled the 5 links with black numbers and the 6 joints with red letters for convenienceAttempt at a solution: I know the mobility equation is M = 3(N-1) – 2(J1) – J2 + R, where N = number of links, J1 is the number of 1 DoF Joints, J2...
14. ### Help Improve our Project for Mobility Challenged People

Dear all We (Maor Rosenberg and my co Vered Waksman) are Materials Engineering students at Ben Gurion University. We are working on a project in the field of mobility equipment for people who are physically challenged (as elderly and temporary/permanently mobility challenged people). As we work...
15. ### Nichrome and Copper Circuit w/ Electron Mobility

Homework Statement In the circuit shown, two thick copper wires connect a 1.5 V battery to a Nichrome wire. Each copper wire has radius R = 0.009m and is L = 0.17m long. Copper has 8.4 \times 10^{28} mobile electrons/m^3 and an electron mobility of 4.4 \times 10^{-3}(m/s)/(V/m). The Nichrome...
16. ### Electrical mobility definition confusion

Hi! According to this http://en.wikipedia.org/wiki/Electrical_mobility, the definition of electrical mobility ##\mu## is: ##\vec{v} = \mu \vec{E}##. But since electrical mobility is always positive, this means that the velocity is always parallel to the E-field regardless of charge. How can...
17. ### Mobility of 2D material, sigma=N*e*mu with N surface density

I have measured the conductivity of a 2D material. I want to use σ=N⋅e⋅μ to find the mobility μ=σ/(N⋅e). https://en.wikipedia.org/wiki/Electron_mobility#Relation_to_conductivity I have measured N using a spectroscopic/imaging technique to get a Surface Density with units [cm^-2]. Mobility...
18. ### Why is graphene placed in a cryostat in research?

I have been told when making transport measurements of graphene it is usually placed in a cryostat and cooled to ~ 4K. However I cannot find any sources that back this up and don't fully understand why it is done in the first place. My thoughts are that it is to measure the carrier mobility...
19. ### Drift tube ion mobility spectrometer

Hello PF, thanks for having me here. I am working in chemistry and we are building a atmospheric pressure drift tube ion mobility spectrometer. The drift tube consists of 20 stacked stainless steel electrodes insulated by PTFE spacers connected via a resistor chain (voltage divider) to produce...
20. ### Measuring the electron mobility of a molecule

Hello PF Let's say I have a device with three layers, A, B, and C, where layers A and C are the anode and cathode. I can measure the IV curves from that device easily. Now let's say I added a fourth layer, D, in between A and B. Layer D interacts with layer B such that it increases it's...
21. ### Band Dispersion and Career Mobility

how the dispersion relation(i.e. E-k relation) affects carrier mobility in metals or semi-metals?
22. ### Increase in doping concentrations resulting in a decrease in mobility?

Homework Statement So in one of our practice problems it states that as we increase the doping concentrations, the result will be a decrease in mobility. However, I thought that when you increase doping concentrations, there will be a higher concentration of carriers available for...
23. ### Piezoelectric Advanced Mobility Suit

Hello I have been thinking about an idea for quite a while. It uses piezoelectric materials to enhance the motions of a human wearer. If someone were to move their leg up, the piezoelectric material will convex and produce a voltage this voltage would be used to trigger a semiconductor that...
24. ### Why does higher mobility = higher frequency of operation (transistors)

I am going to give a presentation on High Electron Mobility Transistors (the ones that use a 2 dimension electron or hole gas), and although I can find many detailed descriptions of the band structures and what causes the 2DEG's high mobility, I haven't found a clear description of the process...
25. ### Electrophoretic Mobility of Hydrophobic/Charged Particles in Saline Solutions

suppose we have a substance that is hydrophobic/hydrophilic and also has some charge on it surface(negative or positive) disspersed in water. if we add some salt different kinds possible(NaCl NaNO3 NaSCN). What is the effect of hydrophobicity and surface charge on Electrophoretic mobility?
26. ### Mobility of couples in academia

Hello, I would like to know what are the chances of a couple getting two permanent academic positions in the same place, since it seems so hard to get a tenure track position? Have you ever tried (and succeeded?) in finding a position in the same city as your wife/husband, and what do people...
27. ### Ionic Mobility & Ionic Size: What's the Connection?

is it true that the ionic mobility increases with the decrease of the ionic size?
28. ### Calculate the lifetime mobility product μτ

Hello, I am trying to calculate the lifetime mobility product μτ for a project. In order to do this I need to calculate the photogeneration. Therefore I need the light intensity and absorption coefficients. I understand how to calculate light intensity, and I have come up with an...
29. ### Mobility of charged particles in classical gas

This is problem 9.2 in solid state physics by Ibach and Luth. Homework Statement Using the stationary Boltzmann equation, show that the mobility of the charged particles in a classical gas is given by \mu = \frac{e \langle v^2 \tau(\mathbf{k}) \rangle}{m \langle v^2 \rangle}...
30. ### Finding electron mobility

The electrical conductivity of copper is 5.96 x 10^7 S/m; its atomic weight is 65.546 AMU; the charge on the electron is 1.06 x 10-19 coulombs; the density of copper is 8.92 g/cm^3. Assume there is one free electron per copper atom. Calculate the mobility in cm^2/volt-sec. This is a...
31. ### Mobility of the electrons

Hi there, i've got a question about the mobility of the electrons in semiconductors and metalls. in a semiconductor the mobilities are ~ 1000 cm²/Vs. In metals the mobilities are in the range of 50 cm²/Vs. what's the origin of that great difference?
32. ### How to calculate conductivity when you know the electron and hole mobility?

Heres the question: A sample of pure silicon, which has four valence electrons is doped with gallium, which has three valence electrons, to give a concentration of 10^23 m^-3. a. Is the material n-type or p-type? b. If the electron mobility is 0.14 m^2/Vs and the hole mobility is 0.05...
33. ### Calculating electron mobility in a rod

Studying for final, this is one of the suggested questions, I have no idea how to approach it. Homework Statement A cylindrical aluminum rod of 2 mm in diameter and 5 cm in length has a thermal conductivity of 237 W m-1 K-1 at 300 K. Calculate the electron mobility in the rod if aluminum...
34. ### Resistivity and Mobility

Homework Statement Assume the mobility ratio u_n/u_p = b in Si is a constant independent of impurity concentration. Find the maximum resistivity \rho_m in terms of the intrinsic resistivity \rho_i. If b = 3 and the hole mobility of intrinsic Si is 450 cm^2/Vs calculate \rho_i and \rho_m...
35. ### Proton mobility vs. conductance in ice

Greetings, I'm trying to understand how protons might move through solid water ice. More specifically this concerns how deuterium/hydrogen ratios are used to date ice core samples drilled into glaciers. On one hand I am told that, once it is deposited from the atmosphere in the form of...
36. ### Solid State Devices - Energy Band Diagram, Mobility, Diffusivity

Homework Statement http://img121.imageshack.us/img121/2910/ssphysucks.th.jpg [Broken] Stuck on 1d Homework Equations Na - Nd = p0 p0 = nie(EF-Ei)/kT kT here is 0.0259 eV n0 = (ni)2/p0 Nv = p0e(EF-EV)/kT Nc = n0e(EC-EF)/kT The Attempt at a Solution I have found: p0...
37. ### Carrier Mobility of a semiconductor

Eg) Silicon Material When we say about mobility of a semiconductor - we basically have to consider its properties etc. One of it is impurities. Here we have to consider its TOTAL Dopant Concentration?
38. ### US not so good on social mobility

I found following quite interesting as well surprising. I always thought US have greater social mobility. http://news.bbc.co.uk/2/hi/americas/8162616.stm
39. ### Mobility of electrons and holes

Problem: Calculate mobilities of electrons and holes (assuming equal) in grey tin, silicon and germanium. Calculate also the mobility that would be necessary for diamond to have an intrinsic conductivity of 10-12 S m-1 if the hole and electron mobilities were equal. Working: \sigma = Nc...
40. ### Mobility of holes and electrons

hi, holes are the absence of electrons in the lattice, right? then how come we say holes have a +ve charge? shouldn't it be zero? also, why is the mobility of electrons more than holes? thanks
41. ### Mobility of Electrons: Why are They More Mobile than Holes?

why the mobility of electrons more than holes despite the fact that electrons have larger effective mass than holes.
42. E

### News The American Dream: Income Equality, Mobility, and Oppotunity

I'm sure you've all heard over and over again that income inequality in the US has increased over the years. This often leads people to conclude that "the rich are getting richer and the poor are getting poorer" and that "income mobility and opportunity are gone (or at least decresing)."...
43. ### Samuel Stupp: Restoring Mobility with Nanofibres

Did Samuel Stupp (Northwestern University) inject/use stem cells when he got the paralyzed mice to walk again or did he just use molecules with he capacity to self assemble into nanofibres once injected into the body? (to get the stem cells to help with the healing, or to do whatever it was that...
44. ### Electron mobility in copper

Hey all, I have a pretty straightforward question about electron mobility in metals. We are given the length of a copper wire, it's radius, the current flowing through it, voltage drop across it, and the proportion of free electrons to copper atoms. I've found the current density...
45. ### News What the hell does class mobility mean?

Seriously, what does it mean and why is it good?
46. ### Mobility and degrees of freedom

Hi guys, Just a quick question. In my lecturers notes, he has mobility and degrees of freedom as different things. With a separate equation for each. However, when I went searching the net for some info because I couldn't understand the notes, I found it to be different. The sites I...
47. ### Mobility Shift Assays: Links & Resources

I am looking for some good links on this particular methodology. Anybody have any?