The number density of free electrons in a copper conductor is estimated as `8.5xx10^(28)m^(-3)`. How long does an electron take to drift from one end of a wire 3.0m long to its other end? The area of cross-section of the wire is `2.0xx 10^(-6)m^(2)` and it is carrying a current of 3.0A.

Explanation

`n=8.5xx10^(28)m^(-3)`
`I=3.0m`
`A=2xx10^(-6)m^(2)`
`I=3.0A`
Current in a conductor `I=nAeV_(d)`
i.e., drift velocity `v_(d)=1/(nAe)=3/(8.5xx10^(28)xx2xx10^(-6)xx1.6xx10^(-19))`
i.e., `v_(d)=0.1103xx10^(-3)ms^(-1)`
time taken for charges to drift across the length of the conductor=t=`("distance")/("speed")`
i.e., `t=3/(0.1103xx10^(-3))=2.72xx10^(4)s`
The time taken for current to drift `= 2. 72 xx 10^(4)s`