## What is Current (I) Measured Relative To

Discussions on classical and modern physics, quantum mechanics, particle physics, thermodynamics, general and special relativity, etc.

### What is Current (I) Measured Relative To

This is addressed to the locals: What is current measured relative to?

Lincoln » July 1st, 2018, 12:57 pm wrote:Current is frame-specific.

If we are talking about a current carrying wire. The current is wire-specific. It flows relative to a wire. If the relative velocity between the wire and the charges is zero. Current is zero. Any ammeter readily shows that current is wire-specific.

Lincoln wrote:If I have an infinite chain of positive charges, with density 1 coulomb/meter and I have them passing me at a rate of 1 meter per second, that's 1 Amp of current.

If a charge or charges pass by you, that's not a current. That's just moving charge or charges. Biot Savart law does not apply to you or to the charges that pass by you, it applies to a wire; as was the context we were discussing it in.

Anyone disagree with my statements? If so, why?
DJ_Juggernaut
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### Re: Surface Tension

DJ_Juggernaut wrote:What is current measured relative to?

It's charge passing through some cross-sectional area (surface). As per Ben Franklin, positive charge for positive current. I put the definition on your earlier thread.

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### Surface or observer?

DJ_Juggernaut wrote:What is current measured relative to?

It's charge passing through some cross-sectional area (surface). As per Ben Franklin, positive charge for positive current. I put the definition on your earlier thread.

I take it that you disagree with Lincoln's take that current is measured relative to an observer.
DJ_Juggernaut
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### Re: Area of Concern

Let the cross-sectional area be the observer (detector) from which we read a measured current. If it moves with the current, no charge will pass through it, thus no current measured in that frame.

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### Re: Area of Concern

Faradave » July 2nd, 2018, 3:00 pm wrote:Let the cross-sectional area be the observer (detector) from which we read a measured current. If it moves with the current, no charge will pass through it, thus no current measured in that frame.

Sounds good to me.
DJ_Juggernaut
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