Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12
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Diffusion Current in a P-n Junction is Greater than the Drift Current in Magnitude - Physics

MCQ

Diffusion current in a p-n junction is greater than the drift current in magnitude

Options

  •  if the junction is forward-biased

  • if the junction is reverse-biased

  •  if the junction is unbiased

  •  in no case.

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Solution

if the junction is forward-biassed

In the forward biassing of a p−n junction, the positive terminal of the battery is connected to the p side of the p−n junction and the negative terminal of the battery is connected to the n side of the p−n junction. As a result, electrons in the n side of the p−njunction are repelled by the negative terminal of the battery and move to the p side, where the positive terminal of the battery attracts the electrons. Similarly, holes from the p side of the p−n junction are repelled by the positive terminal of the battery and move to the n side, where the negative terminal of the battery attracts the holes. Thus, they give diffusion current across the p−n junction. 

In case of reverse biassing, no conduction takes place across the junction because of the diffusion of majority carriers. Hence, there is no diffusion current.
If the junction is unbiased, then diffusion current is initially maximum. But at equilibrium, diffusion current becomes equal to drift current.

Concept: p-n Junction
  Is there an error in this question or solution?
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APPEARS IN

HC Verma Class 11, Class 12 Concepts of Physics Vol. 2
Chapter 23 Semiconductors and Semiconductor Devices
MCQ | Q 10 | Page 417
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