Question

Which of the following characteristics of electrons determines the current in a conductor?

• A. Both drift velocity and thermal velocity
  
• B. Thermal velocity alone
  
• C. Drift velocity alone
  
• D. Neither drift nor thermal velocity
  

Answer 1

The correct option is C Drift velocity alone


Explanation :

• The flow of electrons in a particular direction ( opposite to electric field ) which creates electric current is only due to the drift velocity acquired by free electrons due to electric field applied.
  
• We know, 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 $I=neA{v}_d$
  Where , $n\to$ number density of free electron
  $A\to$ Area of cross-section
  $v_d\to$ Drift velocity
  Hence, $I\propto v_d$
  as 𝑛, $A$ & $e$ are constant.
  
• The thermal motion of electrons is a random motion and it has no preferred direction (its equally distributed in all directions) so, the current created by it is zero.
  
• Therefore, drift velocity determines the current in a conductor.

Hence, option (a) is correct.