# 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-

# 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)

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 carriers.

Quiz on Mobility of Charge Carriers

#### Next Article-

Resistance & Conductance

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