# Homework Help: Variation of Potential outside the PN junction

1. Oct 21, 2015

### Amal Thejus

1. The problem statement, all variables and given/known data
1. We are considering a step junction at equilibrium(no external voltage applied).

2. The potential variation is shown as negative potential at P region(which is shown as constant) and increasing through the transient region to become positive in the n region.

2. Relevant equations
Potential V=Q/4ΠΣ

3. The attempt at a solution
1. As per the equation for potential, the value of potential at the P region should be positive(since Q=positive here) and shown at a higher level than the negative potential in the N region(since Q=negative here).

2.Also the positive potential at P region should drop to a negative value in the transition region next to it(because of the presence of electrons there at equilibrium) and slowly increase to become positive potential as the transient region changes from negative to positive. As the positive region comes to an end the graph should again become negative due to the electrons in the N region.

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2. Oct 25, 2015

### ogg

You have stated no problem. You need to be clearer about what "variation" is. The diagram you provided is NOT "potential variation"; it is a diagram of potential vs distance. Your diagram indicates the potential is NEGATIVE, you claim it is positive. It can not be both. If the change in potential is negative, then the potential is decreasing...is this what you meant? Sorry, I almost never revisit my posts. I suggest if you are still having a problem you re-post since the OP is so old.