# Frequent question: Why mobility is inversely proportional to electric field?

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## Why does mobility decrease when electric field increases?

With increasing temperature, phonon concentration increases and causes increased scattering. Thus lattice scattering lowers the carrier mobility more and more at higher temperature. … Thus, the carriers spend less time near an ionized impurity as they pass and the scattering effect of the ions is thus reduced.

## What is the relation between mobility and electric current?

Mobility is defined as the value of drift velocity over electric field strength. Therefore, higher the drift velocity of the particle higher is the mobility. Which means that the electron will travel at higher speed. E is the electric field.

## Why is mobility independent of electric field?

Electrons move very fast in vacuum. … However, mobility of electrons is independent of applied electric field i.e. change in electric field does not change the mobility of electrons. The SI unit of electric field is V/m, and the SI unit of velocity is m/s. Thus, the SI unit of mobility is m2/ (V.s).

## What is mobility of charge carriers and derive the relation between mobility and electric current?

The mobility of charge carriers in a current carrying conductor can be defined as the net average velocity with which the free-electrons move towards the positive end of a conductor under the influence of an external electric field that is being applied.

## How does mobility depend on conductivity?

Conductivity is proportional to the product of mobility and carrier concentration. For example, the same conductivity could come from a small number of electrons with high mobility for each, or a large number of electrons with a small mobility for each. … Therefore mobility is relatively unimportant in metal physics.

## Why does the mobility of electrons in semiconductor decreases with increasing donor density?

The doping as impurity affects the the mobility of free carriers in the semiconductor material. As the doping increases the mobility decreases.In addition to the scattering of the electrons by doping atoms, the free carriers will be scattered also by the thermal vibration of the lattice.

## What is the relation between mobility and relaxation time?

Mobility is defined at the velocity of the electron per unit electric field. It is the ease with which the electrons can travel in a conductor. So, the mobility of the electrons is directly proportional to the relaxation time of the electron.

## What is the relation between electric field and drift velocity?

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.

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## How does the mobility of a conductor vary with the increase in temperature?

Drift velocity of electrons in a metallic conductor decreases with increase in temperature. Hence, the drift velocity decreased.

## What is conductivity mobility?

Conductivity:- Electricalconductivity is the measure of the ability to carry a current. Electrical conductivity is also known as specific conductance. *Mobility(u):- Mobility is measurement of how quickly an electron pass through a conductor and it’s magnitude is equal to drift speed per unit electric field intensity.

## Why is mobility always positive?

Mobility is always a positive quantity and depends on the nature of the charge carrier, the drift velocity of an electron is very small usually in terms of 103ms1. Hence, at this velocity it will take approx. 17 mins for electrons to pass through a conductor of 1 meter.

## Why does mobility decrease with temperature?

At lower temperatures, carriers move more slowly, so there is more time for them to interact with charged impurities. As a result, as the temperature decreases, impurity scattering increases, and the mobility decreases.

## What do you mean by mobility derive the expression of mobility?

When we have to define mobility, it can be defined as the value of the drift velocity per unit of electric field strength. By analyzing the definition we can conclude that the faster the particles move at applied electric field strength, the larger the mobility. … Mobility: Vd / E, is the Dimensional Formula of Mobility.

## What is conductivity and mobility derive an expression for conductivity in terms of mobility?

Derive an expression for conductivity in terms of mobility. μe = vd / E = e E t /m E = e t / m. We have derived the relation of resistance previously. (

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## Why is the mobility of free electrons greater than that of holes?

The electron mobilty is often greater than hole mobility because quite often, the electron effective mass is smaller than hole effective mass. The relaxation times are often of the same order of magnitude for electrons and holes and therefore, they do not make too much difference.