What is drift velocity? Establish a relation between current and drift velocity?

Explanation

drift velocity = `v_d` number of free e– per unit volume = n

length of conductor = `l` cross sectional area of conductor = A So total free electrons in given conductor = n (`l`A)
Total change ` " " q= n(lA) e," " Time t=( l)/( v_d) `
Now current ` " "I=(q)/(t) " "= ( nlAe)/( (l//v_d) `
Where ` t=l''v_d`
` "neAv"_d " "rArr " "I= "ne"Av_d`