# any possible answers?

Discussion in 'Homework Help' started by c1rcu1ts, Oct 20, 2013.

1. ### c1rcu1ts Thread Starter Member

Oct 19, 2013
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lecturer put this as a bonus question...

A current constituted of a single electron travelling through the centre of a conductor is being studied by a first year engineering student.. The conductor branches into two pathways of equal resistance 1 ohm: Path A and Path B. What do you think the voltage developed across each path should be?

Last edited: Oct 20, 2013
2. ### c1rcu1ts Thread Starter Member

Oct 19, 2013
62
0
can a a single electron even constitute a current?

3. ### WBahn Moderator

Mar 31, 2012
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Yes, a single electron can constitute a current. There are devices in which the capacitance is so small that charge of a single electron is sufficient to raise the voltage enough to stop further current flow until that electron is gated off the capacitor.

The question, though, is probably not really answerable. That depends to some degree on the type of "class" you are talking about. A Circuit I course and a Modern Quantum Physics course would treat this question very differently.

A Circuits course is based on certain underlying assumptions that permit the use of Kirchhoff's Laws as the primary basis for analysis. These assumption do not hold if you are talking about situations in which the discrete, quantized nature of electric charge becomes relevant.

Furthermore, for the circuits that would be discussed in a Circuits I course, the noise current in the resistors would make detecting anything related to a 1e-/s current impossible.

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4. ### shteii01 AAC Fanatic!

Feb 19, 2010
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The current thing is just to throw you off.

The question is the voltage. It is zero.

5. ### #12 Expert

Nov 30, 2010
16,705
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Schroedinger's cat
Hold both wires over a coffee can and see which one the electron comes out of.

6. ### studiot AAC Fanatic!

Nov 9, 2007
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515
The question itself is flawed.

What will the pathways be made of?

In relation to the single electron an assemblage of atoms is too large, and the impedance of free space is 370 ohms.

7. ### #12 Expert

Nov 30, 2010
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Flawed question. I agree. Voltage compared to where? You always need a second point to measure voltage. Maybe the lecturer told the OP, but nobody told me. Even if you did, I wouldn't know the voltage of a single electron. The fact that it is moving makes current, but that doesn't establish what voltage is pushing it.

There. That's a farmers eye view of big city education.

8. ### bwilliams60 Active Member

Nov 18, 2012
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It takes 6.24 billion billion electrons passing a given point in one second to = 1 ampere. You could surmise that you know the amperage is 1/6.24 billion billion to obtain your amperage which is next to nothing or as close as you can be. You have the resistance of 1 ohm so technically because you have two quantites, you should be able to find the third by using Ohm's Law. But since electrons can't split, how does it choose which pathway it takes, and it doesn't matter what it is made of, it's resistance is stated. I would like to hear the answer on this one.

9. ### studiot AAC Fanatic!

Nov 9, 2007
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How many free electrons are there already in a conductor of 1Ω resistance?

I repeat the question is flawed.

10. ### #12 Expert

Nov 30, 2010
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You went straight to the heart of the problem. The voltage must be 1/6.24 billion billion.

11. ### THE_RB AAC Fanatic!

Feb 11, 2008
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Seems straightforward to me.

If there is 1A flowing down a conductor, and gets to a fork, it could be quite possible the 1A flows entirely down one path after the fork, giving a result of 1A in one path and 0A in the other path.

Now with 1A current, it is also possible that 0.5A flows in each path after the fork. What the examiner has done is eliminate that situation by using the fact that a single electron must travel 100% down one path and 0% down the other path, which simplifies the problem.

12. ### #12 Expert

Nov 30, 2010
16,705
7,355
It's not 1 amp, it's one electron.