The numerical problems in this post are based on the drift velocity of electrons and electric current. Electric Current is expressed as *I *= *nAv*e

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

**Numerical problems on Drift velocity of electrons and electric current**

**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 *= *nAv*e

=> **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 worksheet

Now solve the following numerical problems using the same formula.

## Take Away | Suggested reading

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

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

**Suggested Reading**

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

**derive the relationship between drift velocity and current**