Name: Applications of Potentiometer
Uploaded: 2019-07-19
Duration: 4 min 30 s
Description: Since potentiometers are very versatile and handy to use, it is vital to understand their working principle and applications fully. In this video, learn abou...

Question

What is drift velocity of electrons? Show the electric current flowing through a conductor is directly proportional to the drift velocity.

Accepted Answer

Drift velocity can be defined as the average velocity attend by the charged particles in a material due to an electric field. when electrons are subjected to an electric field they do move randomly, but they slowly drift in one direction, in the direction of the electric field applied. The net velocity at which these electrons drift is known as drift velocity.

Consider a conductor of length $l$ and the area of the cross-section $A$ having $n$ electron per unit length, as shown in the figure.

The volume of the conductor $= A l$

$∴$ Total number of electrons in the conductor $=$ volume $\times$ electron density $= A l n$

Total charge contained in the conductor $Q = A l n e$

under the influence of the electric field, free electrons begin to drift in a direction. Time taken by the electrons to cross over the conductor is

$t = \frac{l}{v_{d}}$

where $v_{d}$ is the drift velocity of electrons. Therefore, the current through the conductor is given by

$I = \frac{Q}{t} = \frac{A l n e}{\frac{l}{v_{d}}} = n e A v_{d}$

$\Rightarrow \frac{I}{A} = J = n e v_{d}$

$∵ n, e$ are constant

Therefore, $J \propto v_{d}$

What is drift velocity of electrons? Show the electric current flowing through a conductor is directly proportional to the drift velocity.

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