Number of conduction electrons question

In summary, the problem asks to calculate the number of conduction electrons passing through a given area per second when a current of 1A flows. The solution involves using the current density equation, j = i/A, and the equation for current density in terms of the number of electrons per unit volume, j = nevD. After some calculations, the result is N = i/e, which is equivalent to the number of electrons per second. This result is correct, as confirmed by the conversation.
  • #1
raintrek
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Homework Statement



Calculate how many conduction electrons pass through a given area per second when a current of 1A flows.


Homework Equations



Current density, j = i/A (i=current, A=cross sectional area)
Current desntiy, j = nevD (n=no of electrons per unit volume, e=charge on electron, vD=drift velocity)

The Attempt at a Solution



I've taken an element of volume of length vDt and cross-sect area, A. I've surmised then that the total number of electrons in that area will be N=nAvDt.

All of those electrons will then cross a plane in 1 second, so I've equated j=i/A=nevD, and substituted n from the earlier (bold) equation - n=N/AvD. However, that produces a result of N=i/e=1/e ... doesn't look right! Help!
 
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  • #2
raintrek said:
However, that produces a result of N=i/e=1/e ... doesn't look right! Help!

That looks right to me. How do you think it should look like?
 
  • #3
Look at it a different way, forget about the current density etc.

1A = 1 coulomb/sec

If the charge on one electron is e coulombs, then one coulomb is the charge on 1/e electrons.
 
Last edited:

FAQ: Number of conduction electrons question

How do you determine the number of conduction electrons in a material?

The number of conduction electrons in a material can be determined using the formula n = N/V, where n is the number of conduction electrons per unit volume, N is the total number of atoms in the material, and V is the volume of the material. This formula is based on the assumption that each atom contributes one conduction electron.

What factors affect the number of conduction electrons in a material?

The number of conduction electrons in a material is primarily affected by the number of atoms in the material and the density of the material. Other factors that can influence the number of conduction electrons include temperature, impurities, and the presence of defects in the material's crystal structure.

How does the number of conduction electrons affect the conductivity of a material?

The number of conduction electrons is directly proportional to the conductivity of a material. This means that materials with a higher number of conduction electrons will generally have a higher conductivity. In other words, more conduction electrons means more pathways for electricity to flow, resulting in better conductivity.

Can the number of conduction electrons be changed in a material?

The number of conduction electrons in a material is primarily determined by its atomic structure and cannot be easily changed. However, the number of conduction electrons can be altered by introducing impurities or through the process of doping, which adds or removes electrons from the material's structure.

Are all materials capable of conducting electricity?

No, not all materials are capable of conducting electricity. The ability to conduct electricity depends on the presence of free conduction electrons, which are primarily found in metals and some semiconductors. Insulators, on the other hand, have very few or no free electrons and therefore do not conduct electricity well.

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