Question

I need this problems clear and neat and correct please

4) You have the following scenario: • An electric field points from left to right (along the +x axis) • The electron density decreases as the x-coordinate increases • The hole density decreases as the x-coordinate increases. What are the directions of (Your answer should be either left-to-right or right-to-left or no current.): (a) Electric current carried by electrons due to drift. (b) Electric current carried by holes due to drift. (c) Electric current carried by electrons due to diffusion. (d) Hole current carried by holes due to diffusion.

Answer 1

$\large {\color{Red} Solution}.4$Given:

• The electric field (E) is directed from left to right (+x direction).
• The electron density decreases as the x-coordinate increases.
• The hole density decreases as the x-coordinate increases.

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$\large {\color{Red} (a)}$ To find: The electric current carried by electrons due to drift.

• The drift current is mainly due to the applied Electric field.
• Since the electron is negatively charged , The force on electron due to the applied Electric field will be in a direction  opposite to the direction of applied field (E) .
• So, the electron will move in a direction opposite to the direction of Electric field thereby producing a drift current .
• Since the direction of Electric field (E) is given to be from  left -to-right , So, the direction of electric current carried by electron due to drift will be from  $\large {\color{Red} Right-to-left}$..................Answer

$\large {\color{Red} (b)}$To find:   The electric current carried by holes due to drift.

• The drift current is due to the applied Electric field .
• Since we know that holes are positively charged ,the electric force on the holes will be in the direction of the applied electric field.
• So, the holes will move in the direction of the electric field thereby producing an electric current in the direction of the applied Electric field.
• Since the electric field (E) is in the direction from left to right ,therefore the current carried by holes due to drift will be in the direction $\large {\color{Red} Left-to-Right}$ ​​​​​​​................Answer

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$\large {\color{Red} (c)}$ To find: The diffusion current of electrons.

• Diffusion current is mainly due to the difference in the concentration /density  of charge.
• Diffusion current flow from high charge density to low charge density.

Since the electron density is decreasing from left to right (x-coordinate increases from left to right) ,that means   the electron density will be higher on the left side than that on the   right side. Therefore the current carried by electron due to diffusion will be from  $\large {\color{Red}Left-to-Right}$.

$\large {\color{Red}(d)}$   To find: The current carried by the holes due to diffusion.

Since the hole density decreases from left to right (because x-coordinate increases from left to right ), the hole density on the left side will be higher than that on the right side.

The hole current due to diffusion will flow from high hole density to lower hole density. i.e.

The current carried by holes due to diffusion will flow from $\large {\color{red}Left -to-Right.}$ ​​​​​​​