Practice portal › Current Electricity › Electric Current and Drift Velocity
Asked in RS Academy GUJCET booklet · Drift velocity, mobility and current density
Idea: in a steady state the same current I crosses every cross-section, otherwise charge would pile up somewhere.
I=neAv_d, and n and e are the same all along the wire.
So v_d=I/(neA), that is v_d∝1/A.
In the figure the cross-section grows from the narrow end A to the wide end B.
So the drift speed decreases as the electrons go from A to B.
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