Exploring the Nature and Arbitrariness of Amperes and Epsilon0

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In summary: Thanks. Would you say it's also arbitrary the direction of the electric field, as in the direction of the arrows we see in field lines diverging from positive charges and converging on negative ones, or is that different?Thanks for the question. It's actually not really arbitrary, the field lines are actually pretty close to following the direction of the electric charges, but there's a tiny bit of wiggle room due to the fact that the charges are tiny compared to the distance between them.
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diagopod
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Learning about the nature of current, the Ampere and its role in Epsilon0. I'm assuming that the fact that the Ampere is defined in terms of electrons per second is arbitrary and that it could just as well have been protons per second? And if it had been protons per second, then Epsilon0 would still have the same value and sign because it makes use of Amperes squared, which will come out positive regardless of whether or not Amperes are defined in terms of negative or positive charge per unit time. Is this true?
 
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Ampere is not defined (yet, it's been proposed) in terms of electrons per second. An Ampere is defined as a Coulomb of charge per second.

It's a quantity of charge; the sign of the charge isn't relevant. In fact, when it was defined they still assumed charged flowed from positive to negative, and didn't know that electrons were the primary charge carriers, or the fact that charge comes in discrete quantities.
 
  • #3


What alxm said +

By the definition positive current direction is the direction of positive charge flow. However, like alxm said, it turned out that in most case it is the electrons that are moving and making the current. So the current is kinda "negative". Normally, people speak about current absolute value and indicate the direction. Check Khirhoff's rules and their application.
 
  • #4


alxm said:
Ampere is not defined (yet, it's been proposed) in terms of electrons per second. An Ampere is defined as a Coulomb of charge per second.

It's a quantity of charge; the sign of the charge isn't relevant. In fact, when it was defined they still assumed charged flowed from positive to negative, and didn't know that electrons were the primary charge carriers, or the fact that charge comes in discrete quantities.

that makes perfect sense, thanks for the clarification alxm
 
  • #5


zeebek said:
What alxm said +

By the definition positive current direction is the direction of positive charge flow. However, like alxm said, it turned out that in most case it is the electrons that are moving and making the current. So the current is kinda "negative". Normally, people speak about current absolute value and indicate the direction. Check Khirhoff's rules and their application.

Thanks, yeah, the bit about positive and negative current has always thrown me - absolute value to the rescue :)
 
  • #6


alxm said:
Ampere is not defined (yet, it's been proposed) in terms of electrons per second. An Ampere is defined as a Coulomb of charge per second.

Actually, the ampere is defined in terms of the magnetic force between two long straight parallel wires. If the wires have equal magnitude currents, and are exactly 1 m apart, and the magnetic force between them is [itex]4\pi \times 10^{-7}[/itex] Newtons per meter of wire length, then the current in each wire is exactly 1 ampere.

The coulomb is defined in terms of the ampere, as the amount of charge delivered by a current of one ampere in one second.
 
  • #7


zeebek said:
By the definition positive current direction is the direction of positive charge flow. However, like alxm said, it turned out that in most case it is the electrons that are moving and making the current.

Blame Benjamin Franklin for guessing wrong about the direction of flow of "electric fluid" when rubbing two objects together to charge them. :smile:
 
  • #8


jtbell said:
Blame Benjamin Franklin for guessing wrong about the direction of flow of "electric fluid" when rubbing two objects together to charge them. :smile:

Thanks. Would you say it's also arbitrary the direction of the electric field, as in the direction of the arrows we see in field lines diverging from positive charges and converging on negative ones, or is that different?
 

1. What is the nature of amperes and epsilon0?

The nature of amperes and epsilon0 is that they are both fundamental constants in electromagnetism. Amperes, also known as the ampere constant, represents the strength of an electrical current, while epsilon0, also known as the permittivity of free space, represents the ability of a vacuum to support an electric field.

2. How were amperes and epsilon0 discovered?

Amperes and epsilon0 were both discovered through experimentation and mathematical equations. Amperes were first proposed by French physicist André-Marie Ampère in the early 19th century, while epsilon0 was first calculated by British physicist Michael Faraday in the mid-19th century.

3. Are amperes and epsilon0 arbitrary?

No, amperes and epsilon0 are not arbitrary. They are fundamental constants that have been experimentally verified and have been used in countless scientific calculations and equations. They are not chosen arbitrarily, but rather have been determined through scientific research.

4. How are amperes and epsilon0 related to each other?

Amperes and epsilon0 are related as they both play a crucial role in understanding the behavior of electric fields and currents. Epsilon0 is used in equations to calculate the strength of an electric field, while amperes are used to measure the strength of an electrical current.

5. Can the values of amperes and epsilon0 change?

No, the values of amperes and epsilon0 are considered to be universal constants and are not expected to change. They are defined based on the current understanding of physics and are considered to be fundamental values that do not change over time or in different locations.

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