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  • Bare with me if this is stupid (I've been away from my electrical engineering roots for really long time now). I was wondering if the medium affects the potential difference between any two points. When we say there's a potential difference - it's relative. But when the medium is super-conducting - can the potential difference still exist?

    I read that even the superconductors offer some, but negligible, resistance to the flow of electrons. But under ideal superconducting situations, the two points under consideration would be one and the same (theoretically).

    What I want to know does the medium influence the PD between two points in electrical circuits.
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  • Abhishek Rawal

    Member • Aug 2, 2013

    Kaustubh Katdare
    I read that even the superconductors offer some, but negligible, resistance to the flow of electrons. But under ideal superconducting situations, the two points under consideration would be one and the same (theoretically).

    What I want to know does the medium influence the PD between two points in electrical circuits.
    Nope, In critical temperature there is no resistance.Thus no PD.
    I think SC is obtained at -273 degree C, which is nothing but a parameter of ideal condition.
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  • Jeffrey Arulraj

    Member • Aug 3, 2013

    Super conductors the motion of electrons is in par with the vibration of molecules

    thus the resistance is almost zero

    Here the resistivity drops to zero But no clear statement about the resistance of the material

    But Since resistance is product of resistivity we have theoretically zero resistance in Super conductor
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  • Ahsanul haque

    Member • Aug 5, 2013

    Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature. thanks
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  • Ramani Aswath

    Member • Aug 5, 2013

    By definition there can be no PD in a super conductor for any current. If there is then it is no more a superconductor.
    There was a major national project in India on room temperature superconductivity. Though nothing much came of it.
    125 deg K is the highest temperature at which super conductivity has been recorded.
    There are many commercial system already using superconductors.
    Here are some examples:
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  • Kaustubh Katdare

    Administrator • Aug 5, 2013

    Okay, if there's no potential difference between the two points on a superconductor (at whatever sub-zero temperature), how does the current flow? 😨

    PS: I don't like when it all comes down to the basics.
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  • Anand Tamariya

    Member • Aug 5, 2013

    Conductor by itself doesn't have p.d. Current flows through it when p.d. is applied across it.
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  • Kaustubh Katdare

    Administrator • Aug 5, 2013

    Anand Tamariya
    Conductor by itself doesn't have p.d. Current flows through it when p.d. is applied across it.
    Right. But you need potential difference for the electrons to flow. If superconductors allow the current to flow without potential difference, what determines the direction of the current?
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  • Jeffrey Arulraj

    Member • Aug 6, 2013

    that is taken care by the external potential applied

    Bro Do note Resistance is an intrinsic property based and Potential difference is an extrinsic property

    So Potential applied to the ends of the conductor "Externally" determines the direction of current

    Whereas the molecular arrangement inside of the conductor Plays a role in determining the resistance offered by the conductor
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  • Ramani Aswath

    Member • Aug 6, 2013

    Kaustubh Katdare
    Right. But you need potential difference for the electrons to flow. If superconductors allow the current to flow without potential difference, what determines the direction of the current?
    That is an important question. Another way to look at it is that if a current flows through a resistance, then a PD will appear. Let us consider a super conducting solenoid coil. If a DC source is connected across this with a suitable current limiter, a current starts flowing. If the ends of the coil can now be shorted with a superconducting switch, a permanent magnet will result because the current will keep passing for ever in the coil. The DC supply can now be removed. The direction of current flow will be what was initially given.

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  • ABCD ABCD

    Member • Aug 7, 2013

    Ideally, there will be no PD across any two points. But, practically it's not possible to attain complete superconductivity. So, there will be a PD. This is just my opinion.
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  • Prashant Munshi

    Member • Aug 7, 2013

    Actually Kaustubh has raised the question of if PD will exist on two points on Super Conductor. There will not be since there will be no resistivity. Then the question raised is if there is no PD then why should current flow through a Super Conductor? PD on two points on any conductor comes from the drop in potential due to resistance of the conductor it offers to the current flowing through it. The amount of such potential drop will be calculated as per Ohm's law (neglecting reactance offered by the conductor). But when you ask flow of current through a Super Conductor, it is not the PD between two points (read potential drop) on the conductor which causes current to flow but the current flows for PD applied to the conductor or Super Conductor by a PD generating device, a generator, battery, thermocouple or anything else. The difference is applied potential and drop in potential. Applied potential makes the current flow, the drop in potential is result of the flow of the current. I hope that explains.
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  • Kaustubh Katdare

    Administrator • Aug 7, 2013

    #-Link-Snipped-# : That makes it more clear, thank you!
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  • Jeffrey Arulraj

    Member • Aug 8, 2013

    mreccentric
    Ideally, there will be no PD across any two points. But, practically it's not possible to attain complete superconductivity. So, there will be a PD. This is just my opinion.
    Practical super conductors are in very low temperature till now

    Superconductivity is proven in lower temp and so Zero PD is achievable
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  • ABCD ABCD

    Member • Aug 8, 2013

    Conqueror
    Practical super conductors are in very low temperature till now

    Superconductivity is proven in lower temp and so Zero PD is achievable
    Superconductivity is ideal. At low temperatures, near-to-superconductivity is achieved, but not exact superconductivity.
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