This is - number of charges trough

[something_about]

This is urgent - number of charges trough...

hello



I can't figure out why the next formula tells us the number of charges that move trough cross-sectional area of the conductor.


If a segment of wire has N charges moving with average velocity v, then in time [delta]t the number of charges is

N * A * v * [delta]t


A is the cross-sectional area of the conductor
N is number of charged particles per unit volume

thank you

 

[Gokul43201]

The distance traveled by a charge in time \delta t is, on average, v\delta t[/tex]. <br /> <br /> Construct a plane that cuts through the wire normally. We want to count the number of electrons passing through this plane in some time \delta t. Now, if all the electrons have velocity v, then for an electron to pass through the plane at some time t, it must have been no farther back than v\delta t[/tex] at a time t-\delta t. In other words, only those electrons contained within the cylinder (for a wire of circular cross-section) of length v\delta t[/tex] and area A, at a time t-\delta t will be able to pass through the wall in the ensuing time \delta t[/tex]. This number is simply the product of the volume of this cylinder, Av\delta t[/tex] and the number density, N.