TBR: Speed of Electron Movement

[justadream]

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TBR Physics Book II page 175



“To give you and idea of the drift speed of an electron, consider a household wire (like the ones used for most appliances), but assume that is carries direct current, DC. For a 10 amp current – approximately that of a 1200-watt hair dryer—the electrons take 40 seconds to travel 1 cm along the wire”



I have no conceptual/theoretical basis for this but: Doesn’t that seem really slow?



40 seconds for an electron to go through 1 cm? How does that power anything?

 

[Cawolf]

Drift velocity is slow, but if you have a huge amount of electrons - substantial charge can move.

Consider a copper wire with a density of 8.5 x 10^28 electrons/m^3.

So a 1 cm section of copper wire with a diameter of 5 mm can have 1.66 x 10^22 electrons.

Using the drift velocity you posted.

I = nqAv

I = (8.5 X 10^28 electrons/m^3)(1.6 x 10^-19 C)(1.96 x 10^-5 m^2)(2.5 x 10^-4 m/s) = 66 A !!

The electrons may travel slow, but their sheer number allows for substantial current flow.