# Numericals on Drift Velocity class 12

Last updated on June 25th, 2023 at 02:30 pm

In this post, you will find solved **Numericals on drift velocity for class 12**. These numerical problems are based on the drift velocity of electrons and electric current.

( see the **derivation of electric current and drift velocity equation** )

**Formulas Used**

Electric Current

I=nAve

Mean drift velocity v = I /[nAe]

where *A *= area of cross-section of the conductor, n = number of electrons per cubic meter, *e *= charge on each electron, and* v = drift velocity of the electron*.

**Numericals on Drift Velocity for Class 12** [solved]

1 ] A copper wire has a cross sectional area of 7.85 x 10^{-7}m^{2}. The number density of copper is 8.5 x 10^{28}m^{-3}. Calculate the mean drift velocity of the electrons through the wire when the current is 1.4 A.

**Solution:**

The equation to use: ** I = nAve** ( see the

**derivation of the drift velocity equation**)

=>

**mean drift velocity = v = I/(nAe)…. ……… (1)**

As per the problem statement, A=7.85 x 10^{-7} m^{2}

n=8.5 x 10^{28} m^{-3}

and I = 1.4 A

We know, e=1.6 x 10^{-19}

Putting all the values in equation 1, we will get:

v= 1.31 x 10^{-4} m/s

**Drift velocity Numerical Extra Questions as exercise**

Now solve the following numerical problems using the same formula.

**Take Away | Suggested reading**

Here we have solved numerical problems on the drift velocity of electrons and electric current.

You can go through the following related and suggested posts for a better understanding of the topic.

**drift velocity and current – how slow drift velocity causes high-speed current**