Question

If the average drift speed of an electron is very slow, how can there by a current on the order of 1 or 2 ampere in a circuit if the drift speed is only about 1 meter per hour?

Answer 1

The simple answer is that there are many many charge carriers are moving in the direction. Yes the drift velocity is low. But to flow large amount of current it not only depends upon the drift velocity. At a particular instant there are many and many charge carriers passing through a cross sectional area per unit time. Which result in a significant amount of current.

Mathematically,

I = nqAVd

Where, I is the current

n is the number of charge carriers

q is the charge carrier

A is the cross sectional area

Vd is the drift velocity of electrons

In a conductor the electrons follow zig zag path therefore there drift velocity is low but by increasing the number of charge carrier there is a good amount of current flowing through the conductor.

For example -  In a 0.01 cm-long 14 gauge copper wire, there would be as many as 3.51 x 10^20 copper atoms. Each copper atom has 29 electrons out of that 11 are valence electrons. If we assume that each copper atom contributes just a single electron, then there would be as much as 56 coulombs of charge within a thin 0.01-cm length of the wire. With that much mobile charge within such a small space, a small drift speed could lead to a very large current.