On applying an electric field of intensity 10 V/cm across a semiconductor at a certain temperature the average drift velocity of free electrons is measured to be 70 m/s. Then the electron mobility is

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ESE Electronics 2011 Paper 1: Official Paper
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  1. 7 × 104 cm2/Vs
  2. 700 cm2/Vs
  3. 7 cm2/Vs
  4. 700 cm/Vs

Answer (Detailed Solution Below)

Option 2 : 700 cm2/Vs
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Detailed Solution

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Concept:

Mobility: It denotes how fast is the charge carrier is moving from one place to another.

It is demoted by μ.

Mobility is also defined as:

\(μ=\frac{V_d}{E}\) cm2/Vs     ------(1)

Where,

Vd = Drift velocity

E =  field intensity

Calculation:

E = 10 V/cm

Vd = 70 m/s = 7000 cm/s

From equation (1):

\(μ=\frac{7000}{10}\)

μ = 700 cm2/Vs

Note: 

Electron mobility is always greater than hole mobility, 

Hence electron can travel faster and contributes more current than a hole.

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