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Electrical riddle no.6 – Forces between two current elements and Newton's third law

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  • #59

      Consider two non parallel wires each carrying a current which located at one plane surface.

      According to electromagnetic theory, the forces between two straight and solid wires mentioned can be estimated as follow:

      F= i . (L x B)

      Where the "F" is force vector that applied to each wire and "L" and "B" are current path vector and flux density vector respectively. Also "i" is amount of current and "x" is vector multiply symbol.Therfore the vector of forces are perpendicular to "L" or wires body.
      Whereas two wires are not parallel, generally that mentioned forces which applied to wires can not be parallel. As you see we have two piece of material that apply two mutual forces to each other which are not alien and this is inconsistent with Newton's third law seemingly.

      What is your opinion?

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    • Author
    • #1173

        Basic definition The classical definition of angular momentum as L=r


          I think we shall try to transfer our knowledge content to others by easiest form. Indeed the information package isn’t knowledge and it shall be reproduced by creative thinking by others. Please kindly explain conclusion of your mathematical discussion with easier language. Also I think we can find problem answer in classical physics or electrical engineering field too.


            According to electrical engineering experience, two free wires carrying currents can not stable non parallel, and applied electromagnetic torque to each wire rotate them and they will be parallel after short time.Therefor in non parallel configuration of wires we need to assume one supplementary mechanical force in system which we were not considered it. Of course in free wires moving duty we have involved with problem yet. In that condition because of magnetic field variation, the mass of magnetic field change due to wires moving. Therefore the essential principle of survival momentum is fulfilled and we can forget that inconsistent (action and reaction forces) temporarily. What is your opinion?


              I dont understant. Why dont you answer clearly ? if you know the answer.


                Our main discussion (in electrical engineering field) is regarded static condition of system. But about your comment, I can add as follows: The law of conservation momentum is one of essential law in classic and modern physics that shall not contravene. Also as you know the electromagnetic field similar to other forces field is a form of energy and energy is equal to mass, therefore the changing of electromagnetic field cause mass or momentum changing.

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