# Does Distance Matter in the Definition of an Electron Volt?

• davidong3000
In summary, the definition of an electron volt is the kinetic energy gain when an electron moves through a potential difference of 1 volt. The distance between the positive and negative sources does not affect this definition because the electrostatic force also changes with varying distances. The same concept applies to a ball rolling down an inclined plane with varying angles. In the case of a wire, the charge carriers do not experience acceleration, so the voltage and current remain constant regardless of where along the wire they are measured. In a scenario where electrons and protons add up to 1 volt and move towards each other in space, the kinetic energy gained is not necessarily 1 electron volt, as the constant and static field changes as they get closer.

#### davidong3000

got a question about the definition of an electron volt. The net says that it is the kinetic energy gain when an electron moves thru a potential diference of 1 volt. But the distance between the positive and negative source of that 1 volt... does it not matter or affect the definition? Because this distance is never mentioned in the definition.

An electron that is stationary but then suddently exposed to a + and - charge source 1 meter apart and the - source positions it self right on the electron so the electron flies to the + source and at that instant when it reaches the + charge source has a total kinetic energy x which we all think is 1 electron volt right? Would the result be diferent if instead of 1 meters the distance between the + and - charge sources was 2 meters or 100 meters?

Nothing is mentioned also about how long the electron has to be exposed to the 1 volt to gain 1 electron volt.

Dave

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davidong3000 said:
got a question about the definition of an electron volt. The net says that it is the kinetic energy gain when an electron moves thru a potential diference of 1 volt. But the distance between the positive and negative source of that 1 volt... does it not matter or affect the definition? Because this distance is never mentioned in the definition.

An electron that is stationary but then suddently exposed to a + and - charge source 1 meter apart and the - source positions it self right on the electron so the electron flies to the + source and at that instant when it reaches the + charge source has a total kinetic energy x which we all think is 1 electron volt right? Would the result be diferent if instead of 1 meters the distance between the + and - charge sources was 2 meters or 100 meters?

Nothing is mentioned also about how long the electron has to be exposed to the 1 volt to gain 1 electron volt.

Dave

It does not matter because the electrostatic FORCE also changes as you vary the distance between the two fixed potential Thus, the accelerating force differs with different distances between the two potential.

Think of a ball rolling down an inclined plane. The potential difference is defined as the height. However, you can make the ball roll down an inclined of various angles. This will then dictate how far the ball actually moved. Yet. no matter what this distance is, the KE gained is still the same, since it is going in between two fixed potential in all cases.

Zz.

ZapperZ said:
It does not matter because the electrostatic FORCE also changes as you vary the distance between the two fixed potential Thus, the accelerating force differs with different distances between the two potential.

Think of a ball rolling down an inclined plane. The potential difference is defined as the height. However, you can make the ball roll down an inclined of various angles. This will then dictate how far the ball actually moved. Yet. no matter what this distance is, the KE gained is still the same, since it is going in between two fixed potential in all cases.

Zz.
how come then dc current in a wire experience the same voltage no matter where along the wire u measure it's voltage ?

also the dc current along the wire has the same amp no matter where along the wire u measure it.

lastly, if a bunch of electrons and protons adding up to 1 volt between them started moving toward each other, at the moment they hit each other, will they both gail 1 electron volt worth of kinetic energy ?

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davidong3000 said:
how come then dc current in a wire experience the same voltage no matter where along the wire u measure it's voltage ?

also the dc current along the wire has the same amp no matter where along the wire u measure it.

The charge carriers in a wire, on average, do not experience an "acceleration". The drift velocity is a constant value, not increasing. So you cannot make the same comparision here with free charges. Why? Because you are ignoring a whole buch of scattering effects that occurs in a conductor that you do not consider in a free particle.

Zz.

ZapperZ said:
The charge carriers in a wire, on average, do not experience an "acceleration". The drift velocity is a constant value, not increasing. So you cannot make the same comparision here with free charges. Why? Because you are ignoring a whole buch of scattering effects that occurs in a conductor that you do not consider in a free particle.

Zz.

oh ok i just thought maybe the wire extends the voltage strength at the source .

last question , if a bunch of electrons and protons adding up to 1 volt between them started moving toward each other, at the moment they hit each other, will they both gain 1 electron volt worth of kinetic energy ?

davidong3000 said:
oh ok i just thought maybe the wire extends the voltage strength at the source .

last question , if a bunch of electrons and protons adding up to 1 volt between them started moving toward each other, at the moment they hit each other, will they both gain 1 electron volt worth of kinetic energy ?

I don't understand that question. Electrons and protons adding up to "1 V"? Are they "moving" due to each other's field? If they are, then you should consider that each of them is not seeing a constant, static field as they get closer.

Zz.

ZapperZ said:
I don't understand that question. Electrons and protons adding up to "1 V"? Are they "moving" due to each other's field? If they are, then you should consider that each of them is not seeing a constant, static field as they get closer.

Zz.

yeah their in space and moving toward each other. 2 clumps of oppositely charged plasma clouds speeding toward each other in 0 g vacuum. I am guessing maybe 0.5 ev is attained prior to the formation of hydrogen gas cloud?

they started off with 0 speed ofcoarse.

davidong3000 said:
yeah their in space and moving toward each other. 2 clumps of oppositely charged plasma clouds speeding toward each other in 0 g vacuum. I am guessing maybe 0.5 ev is attained prior to the formation of hydrogen gas cloud?

But there is no symmetry here. A proton is humongously heavier than an electron. Take an electron and a proton, separate them by a distance and let them go. Where do you think the electron will be when they collide? Where do you think the collision point will be when compared to the original position of the proton? Why do you think this is similar to the OP when the field that the electron sees isn't a constant as when it is in a fixed potential?

Zz.

ZapperZ said:
But there is no symmetry here. A proton is humongously heavier than an electron. Take an electron and a proton, separate them by a distance and let them go. Where do you think the electron will be when they collide? Where do you think the collision point will be when compared to the original position of the proton? Why do you think this is similar to the OP when the field that the electron sees isn't a constant as when it is in a fixed potential?

Zz.

oh, replace the protons with positrons then.

davidong3000 said:
oh, replace the protons with positrons then.

But that still doesn't change the fact that the charges are not moving in a uniform field. Try this:

Put -q at x=-l. Put +q at x=+L, where L>l.

Now bring +q from L to l. What is the work done here? This is essentially similar to your original question.

Now look at another scenario. Put -q at x=-L, and put +q at x=+L as before. Now let them together move towards each other until -q reaches -l and +q reaches +l. Again, calculate the work done here.

You'll see that those two cases will not give you the same answer EVEN when they both end up at the same location from each other.

Zz.

ZapperZ said:
But that still doesn't change the fact that the charges are not moving in a uniform field. Try this:

Put -q at x=-l. Put +q at x=+L, where L>l.

Now bring +q from L to l. What is the work done here? This is essentially similar to your original question.

Now look at another scenario. Put -q at x=-L, and put +q at x=+L as before. Now let them together move towards each other until -q reaches -l and +q reaches +l. Again, calculate the work done here.

You'll see that those two cases will not give you the same answer EVEN when they both end up at the same location from each other.

Zz.

yes i agree, i said that the 2nd experiment would probably give 0.5 ev for each electron. but i suspect that's wrong too. how many ev will the electrons and positrons gain prior to annihilation?

## 1) What is an electron volt?

An electron volt (eV) is a unit of energy commonly used in atomic and nuclear physics. It is defined as the amount of energy gained by an electron when it is accelerated through a potential difference of one volt.

## 2) How is distance related to an electron volt?

The distance between two charged particles affects the amount of energy required to move an electron between them. This is because the electric force between two charged particles decreases as the distance between them increases. Therefore, the distance between particles is a factor in the definition of an electron volt.

## 3) Does the distance matter in the definition of an electron volt?

Yes, the distance between charged particles is a crucial factor in the definition of an electron volt. As mentioned before, the electric force between two charged particles decreases as the distance between them increases, and this affects the amount of energy required to move an electron between them.

## 4) How is the distance between charged particles measured in relation to an electron volt?

The distance between charged particles is typically measured in nanometers (nm) when discussing electron volts. This is because the electric force between particles is strongest at a distance of 1 nm.

## 5) Are there any other factors besides distance that affect the definition of an electron volt?

Yes, besides distance, the charge of the particles and the electric potential between them also play a role in the definition of an electron volt. The greater the charge of the particles and the higher the electric potential difference, the more energy an electron will gain when moving between them.