All Questions

Filter by
Sorted by
Tagged with
40
votes
3answers
12k views

Will the volt, ampere, ohm or other electrical units change on May 20th, 2019? [duplicate]

When watching a video by Veritasium about the SI units redefinition (5:29), a claim that the volt and unit of resistance (presumably the ohm) will change by about 1 part in 10 million caught my ...
2
votes
2answers
187 views

Is there (or was there) a unit of electric current based on Avogadros number or Coulombs constant?

This has to do with the SI definition of the Ampere. Why the quantity $2*10^{-7} $ Newtons in particular? It would make more sense to define 1 Ampere = 1 mole of electron charge per second. Which ...
0
votes
1answer
619 views

Why is a Coulomb not a fundamental unit? [duplicate]

Why is a coulomb not a fundamental unit but an ampere is considering that a coulomb is more ' fundamental '?
6
votes
4answers
835 views

Why are electrical units (specifically, electrical current) considered a base unit?

Note: this is NOT a question why current is the base unit as opposed to charge—that’s because measuring $1 \ \mathrm{ A }$ through a wire is easier to measure in a lab than is $1 \ \mathrm{ C }$ in ...
1
vote
0answers
76 views

Why is ampere defined with $2 . 10^{-7}$? [duplicate]

The formal definition of the Ampere is that it is the constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed one ...
4
votes
1answer
269 views

What's the motivation to define the unit of current as fundamental in SI system? [duplicate]

The charge in electromagnetism seemingly plays the same role like mass in the Newtonian mechanics.But why we define the current unit (Ampere) in SI system as the fundamental rather than charge unit?
3
votes
2answers
871 views

Definition of Ampere

On Wikipedia it says: This force is used in the formal definition of the ampere, which states that it is "the constant current that will produce an attractive force of $2 × 10^{-7}$ newton per ...
52
votes
2answers
19k views

Why is the ampere a base unit and not the coulomb?

I always thought of current as the time derivative of charge, $\frac{dq}{dt}$. However, I found out recently that it is the ampere that is the base unit and not the coulomb. Why is this? It seems to ...