Mobility of Charge Carriers | Formula

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Electric Current-

 

Before you go through this article, make sure that you have gone through the previous article on Mechanism of Current Flow.

 

We have learnt-

  • When a potential difference is applied across the ends of a conductor, an electric field is created inside it.
  • The electric field applies an electric force on the free electrons inside it.
  • As a result, they start drifting in a preferred direction and the flow of current starts.
  • The drift velocity of free electrons is given by the formula-

 

 

In this article, we will learn about mobility of charge carriers.

 

Mobility of Charge Carriers-

 

The conductivity of any material is due to its mobile charge carriers. These may be-

  • electrons in metals
  • positive and negative ions in electrolytes
  • electrons and holes in semiconductors

 

The mobility of a charge carrier is defined as the drift velocity acquired by it in a unit electric field.

 

The mobility of a charge carrier is denoted by the symbol μ and is given by the formula-

 

(Equation-01)

 

Characteristics-

 

  • The SI unit of mobility is m2V-1s-1.
  • The dimensional formula of mobility is [M-1L0T2A1].

 

Deriving SI Unit Of Mobility-

 

From equation-01, the mobility of a charge carrier is given by-

 

 

So, SI unit of mobility is given by-

 

 

Deriving Dimensional Formula Of Mobility-

 

From equation-01, the mobility of a charge carrier is given by-

 

 

So, dimensional formula of mobility is given by-

 

 

Relation Between Electric Current & Mobility For A Conductor-

 

We know, the relation between electric current and drift velocity of charge carriers is given by-

 

(Equation-02)

 

Also Read- Derivation of Relation Between Electric Current & Drift Velocity

 

From equation-01, we have-

 

(Equation-03)

 

Using Equation-03 in Equation-02, we get-

 

 

This is the required relation between electric current and mobility of charge carrier.

 

Read the next article on-

Resistance & Conductance

 

Get more notes & other study material of the Chapter Current Electricity.


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