IIT JEE , AIEEE Forum - Physics , Modern Physics - Q.1> Differentiate b/w drift current and diffusion current in a p-n junction

v_gurucharan

Q.1> Differentiate b/w drift current and diffusion current in a p-n junction

eragon007

in a p-n junction the drift current is the current produced due to the movement of e-
diffusion current is the movement of holes

Taara

Q.1> Differentiate b/w drift current and diffusion current in a p-n junction

drift i e- p to n.

diffusion e- n to p. holes opp

Nithy

diffusion current - flow of e- from n side (where they're majority)
to p side (minority) and holes frm p to n. occurs naturally at initial

drift is e- p to n . the reverse. due to electric fiels set us bcoz as diffusion takes place ionised cores( + ve) left behind n side so e- in p side attracted..
takes place after diffusion..

later eq attained.

hope its clear!!!!!!!

feynmann

Formula for drift current-density j =E

formula for diffusion hole - current density j = q Dp p/x ( along x-axis )

Dp = diffusion coeff for holes

similarly for electrons .

Initially only diffusion is present ( due to unequal concn of holes and electrons across the jn ) After sometime ,as the carriers have come across the jn they create an electric field which creates a drift current .

In the steady state drift current = diffusion current , so that no net transfer of charge occurs across the jn .

v_gurucharan

What is dynamo effect?

v_gurucharan

Drift current is electrons and holes responding to an applied electric field. Holes move in the direction of the electric field while electrons move opposite the electric field. This occurs as long as there are carriers available. Diffusion current is holes and electrons moving from areas of high concentration, where they are the majority carrier, to areas of low concentration, where they become minority carriers. This occurs until they are uniformly distributed. Unlike drift, diffusion takes place without an electric field being present.

dev_22oct

Drift is, by definition, charged particle motion in response to an applied electric field. When an electric field is applied across a semiconductor, the carriers start moving, producing a current. The positively charged holes move with the electric field, whereas the negatively charged electrons move against the electric field. The motion of each carrier can be described as a constant drift velocity, v_d.

Diffusion is the process of particles distributing themselves from regions of high concentration to regions of low concentration. If this process is left unperturbed, there will eventually be a uniform distribution of particles. Diffusion does not need external forces to act upon a group of particles. The particles move about using only thermal motion. If we let the particles be carriers, so as they move around they take charge with them. The moving of charge will result in a current. We call this current due to diffusion.

dev_22oct

The difference between drift current and diffusion current is that drift current depends on the electric field applied: if there's no electric field, there's no drift current. Diffusion current occurs even though there isn't an electric field applied to the semiconductor

Nithy

dynamo effect is movement of molten materials in the core i mean the "currents" that r said to be set up in earth's core

which is postulated to cause earth's magnetism...

intensive reasearch seems to be going on... doesn't fully explain magnetic effect though!

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