What affects the speed of electrons in a resistor?

If two resistors are connected in series, they both have the same current ; same amount of electrons passing at a point per second.

Then if one resistor is a thin wire and one resistor is a large wire, do electrons travel faster in a thin wire or a large wire of same material and external conditions.

Is it affected by the electric field strength? So Voltage / Length of resistor.

^If it is, then currentxresistance / length = current x resistivity x length/(area x length) = current x resistivity /area .So thinner wires have a higher electric field strength hence electrons travel faster, is this true?


note: it feels like the oppsoite of what you would think as it feels like electrons will have a easier time travelling through wires of large cross-sectional area.

  • \$\begingroup\$ you can suppose current is flow of water and your resistors are channel.hope this is helpful. \$\endgroup\$ – Panda Nov 20 '14 at 9:57
  • \$\begingroup\$ hmm,,... does water slow down at large channels or tight channels \$\endgroup\$ – user143525 Nov 20 '14 at 9:59
  • \$\begingroup\$ what do you think?:D \$\endgroup\$ – Panda Nov 20 '14 at 10:21
  • \$\begingroup\$ you know current is constant and so flow of water is constant so you have AV=A'V'. \$\endgroup\$ – Panda Nov 20 '14 at 10:21
  • \$\begingroup\$ Wait does this work, as current is constant, in thinner wires, there is less area for charge to travel, so more charge has to travel in the same amount of time so velocity is higher then in a thicker wire. \$\endgroup\$ – user143525 Nov 20 '14 at 10:27

Basically, it can be explained by "Mechanics".

The voltage source at the resistor's ends, create a electric filed, assume the filed is uniform, and their is no other force on the particle, then

$$ \vec{F_{e}}=q\vec{E}=m\vec{a} $$

So, the speed of the charge must have some relations with the voltage drop on the resistor.

Actually, the speed of the charge particle travel in a conductor, is called "drift velocity", in that link, it gives the drift speed equation.

enter image description here

If a thin wire and a large wire, given same voltage source, same material, and their main difference is only they have different area of cross-section. If the current flow in them are same, because

$$ I_{avg}=nqv_{d}A $$

Where \$v_{d}\$ is the drift speed, \$n\$ is the charge-carrier density, \$q\$ is the charge on the charge-carrier, \$A\$ is the area of cross-section of the conductor. So the drift speed in the thin wire must greater then the "large wire".

  • \$\begingroup\$ Good, of course the thermal velocity of electrons in conductors is much faster than the drift velocity. \$\endgroup\$ – George Herold Nov 20 '14 at 13:16
  • \$\begingroup\$ Yes, drift velocity describe the net velocity of electrons in a certain direction under an applied field. But thermal velocity has a "random" behavior. \$\endgroup\$ – diverger Nov 20 '14 at 13:25

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