Answer to Question #84046 in Electric Circuits for Arjad

Question

How does dirty speed of electrons change as they move through resister?
Increases or decreases or remains the same?

Answer 1

First, let's assume that "dirty speed of electrons" is actually "drift speed of electrons". Now recall an expression for the drift speed of electrons

$$v$$

:

$$v=I/enA,$$

where

$$I, e, n, A$$

- current, the elementary charge, number density of electrons, cross-sectional area of a conductor respectively. According to the formula:

1) Since any resistor has to be connected in series with the wires, current is the same in the wires and the resistor.

$$I$$

is constant.

2) Number density of electrons depends on the material, but since resistors are used to reduce current, we can conclude that for resistors

$$n$$

is smaller than for the common aluminum/copper wires. The drift speed may increase at this point.

3) As we said, resistors intend reducing currents. It means that

$$A$$

is smaller for wires in resistors than for wires on the outside of resistors (of course if you pick a correct resistor). The speed thus increases at that point.