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What will happen if two ends of diode are joined?

  1. Dec 12, 2012 #1
    Here i am discussing about diode made up of p-n junction.

    what will happen if we join two ends of diode?
    Due to diffusion, there is a potential difference across depletion region.if we consider this as a battery(can we do so?) then there will be flow of continous current through the external joint.
    But i think there will no flow of current or very little flow of current because flow of current will cause I^2 R losses, since our source has no stored energy in it so it can not transfer a continuous supply of current.

    please tell me your answer. and also don't forget to write where am i wrong in my explanation(i know that is wrong)...
  2. jcsd
  3. Dec 12, 2012 #2


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    you have just shorted out the diode so the current will flow through the short circuit

  4. Dec 12, 2012 #3


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    Try it, and use your tools (hopefully a multimeter at a minimum) to see what is going on. Diodes are cheap and plentiful, so the experiment won't cost you much.
  5. Dec 12, 2012 #4


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    The width of the PN junction changes until the potential minimises and then no more current will flow.
  6. Dec 12, 2012 #5

    See attachment.

    No, a battery is a chemical to electrical energy converter. The diffusion potential will be limited by the bound uncovered charges left behind after diffusion. The mobile electrons from the Nd dopant will diffuse into the p-type and annihilate a hole, leaving behind a Nd+ bound ion. The mobile holes from the Na dopant will diffuse into the n-type and annihilate a electron, leaving behind a Na- bound ion. These bound ions eventually form a back voltage (Vj or Vbi when the external voltage is zero) that keeps the mobile holes and electrons from crossing PN junction barrier. As you can see from the attachment, when no external voltage is applied, the junction voltage equals the sum of the contact potientials Vp and Vn. No current will exist unless an external voltage is applied across the PN contacts.


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    Last edited: Dec 12, 2012
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