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# repulsive or attractive force?

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if i set up a wire loop J with a current I flowing clockwise, and attach wires AB, BC, CD & DG as seen in the picture

the current on wires AB, BC, CD & DG i would expect to be 0.5I while the portion of loop J (portion AC and CG of wire loop J)adjacent to wires AB, BC, CD & DG also carries 0.5I

my question: are the forces between the current in each wire and current loop J attractive to each other? and are the forces between the currents in the wires repulsive or attractive?

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Why is this speculation?

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Posted (edited)

2 hours ago, swansont said:

Why is this speculation?

Maybe because Speculation is repulsive?

Edited by michel123456

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18 hours ago, DandelionTheory said:

the current on wires AB, BC, CD & DG i would expect to be 0.5I while the portion of loop J (portion AC and CG of wire loop J)adjacent to wires AB, BC, CD & DG also carries 0.5I

That will only be true if you arrange for the resistance of ABC and the arc AC to be equal (e.g. make the wires AB and BC have ~1.4x greater cross-section)

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Posted (edited)

20 hours ago, DandelionTheory said:

are the forces between the current in each wire and current loop J attractive to each other? and are the forces between the currents in the wires repulsive or attractive?

I say the currents causes magnetic fields that creates attractive force between the cables.

A few assumptions are made, listing them so others may spot flaws. First I assume the currents actually are able to flow the way you describe. Second I assume the currents' directions will be as in picture below; I've just added more arrows to your picture. Then I also assume the loop is large so that we can neglect attraction across the loop such as AB <-> DG.

The above allows me to do an estimate without requiring the usage of the general case formula for Ampere's law*:
Since currents are flowing roughly in the same direction in cables they attract

I do not have the time to try to apply the formula to check, so I boldly provide the answer from the reasoning regarding the geometry. Hopefully good enough for further discussions.

*) General case:

Edited by Ghideon

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The r12 convention tends to confuse me. I'd go with applying twice the right-hand rule. One for field/source and a second one for Lorentz force law:

$\boldsymbol{B}_{1}\sim\boldsymbol{\nabla}\times\boldsymbol{j}_{2}$

$\boldsymbol{F}_{1}\sim\boldsymbol{j}_{1}\times\boldsymbol{B}_{1}$

The force on j1 is towards j2.

Resp. for 2 <-> 1

I assume with Ghideon that there aren't, e.g. power sources that invert the current along AC or CG along either wire.

Neither do I see how this is a speculation.

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7 hours ago, swansont said:

Why is this speculation?

!

Moderator Note

Moved to Physics.

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On 6/2/2020 at 7:53 AM, swansont said:

Why is this speculation?

"and are the forces between the currents in the wires repulsive or attractive?"

my speculation.

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2 minutes ago, DandelionTheory said:

"and are the forces between the currents in the wires repulsive or attractive?"

my speculation.

No, that’s a question.

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Posted (edited)
59 minutes ago, DandelionTheory said:

"and are the forces between the currents in the wires repulsive or attractive?"

my speculation.

Just to reduce the risk for any misunderstandings regarding my answer: There are no time dependencies; forces are constant. The forces are also cancelling each other.

Edited by Ghideon
grammar

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