In a circuit, if the voltage is doubled, what happens to the drift velocity?
It will essentially double. The Coulomb scattering cross section decreases with speed but for typical voltages the change is very slight.
thanks. Does the drift speed half if the length of wire doubles?
If you couldn't tell from the previous response,
You are supposed to at least tell us how you're thinking ...
How would a tiny charge deep inside an opaque wire find out
how long the wire was?
OK i just need to know what factors vary drift velocity. I am not very smart, my teacher is rubbish and I have exams in a week so im quite frustrated. So length doesnt change the speed? Voltage increases the drift speed as electrons gain more energy? Increasing cross-sectional area decreases the drift speed as there is a larger area for more collisions therefore slowing down the electrons
No, the drift velocity is causally determined by LOCAL quantities:
the Electric Field, the charge carrier density, the density, size,
and mass of the NON-mobile atoms (and the Temperature).
Voltage only has an effect on drift velocity if it influences the local E-field.
It's the E-field that accelerates electrons, before they collide and start again.
Cross-sectional Area only affects drift velocity if it decreases R thereby decreasing V (if current is held constant) thereby decreasing the local E-field.
Increasing the length might (if Voltage is held constant) change the local E-field, in what way?
I have a question regarding drift velocity. Paul Drude originally had the drift velocity given by
v =(q*E/m*2)*t (1)
but then the factor of 2 was dropped and now most textbooks write the drift velocity as
v = (q*E/m)*t (2)
My question is was it measurement of the actual current in a wire that led to the dropping of the factor of two ? In other words Drude's formula disagreed with observation so equation (2) was adopted.
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