What Force Causes Drift Velocity Increase in Wires of Different Diameters?

[Himal kharel]

consider two wires of different diameter. when current enters from that of greater diameter to lesser diameter drift velocity increases. which force causes it to increase?

 

[A.E]

it is really simple.
we have,current(I) through a conductor of the crossectional area of A is the product of the drift velocity(v) of the moving charges ,the area(A) and number of electrons(n)*the charge of a electron(e).hence
I=venA
or, v=I/(enA)
this relation shows that drift5 velocity is inversely proportional to the area of crosssection of the conductor.Hence if area decreases drift velocity increases.
HOPE THIS HELPS HIMAL

 

[chrisbaird]

I don't think there's an external force involved, as it seems you have in mind, rather conservation of energy causes the drift velocity to increase, similar to http://en.wikipedia.org/wiki/Bernoulli%27s_principle" in fluid dynamics.