Chapter-3|Current Electricity| NCERT 12th Physics:
We consider a conductor of length l and A be the uniform area of cross-section.
Volume of conductor V= Al
If n be the number of free electron per unit volume, then
Total number of free electron in conductor= nAl
If e is the charge of an electron, then the total charge of all electron in conductor
q= nAle -(I)
Time taken by the free electron to cross the length l of the conductor
