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Thread: Resistance of a conductor

  1. #1 Resistance of a conductor 
    Forum Freshman ScubaDiver's Avatar
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    What are all the possible ways to change the resistance of a conductor?

    I know the basic three

    1. Change the cross sectional area of the conductor
    2. Change the length
    3. Change the temperature

    Are the other ways?

    I was thinking that situating the conductor in a magnetic field would cause the charge carriers to bunch on one side of the conductor and change its resistance.


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  3. #2 Re: Resistance of a conductor 
    . DrRocket's Avatar
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    Quote Originally Posted by ScubaDiver
    What are all the possible ways to change the resistance of a conductor?

    I know the basic three

    1. Change the cross sectional area of the conductor
    2. Change the length
    3. Change the temperature

    Are the other ways?

    I was thinking that situating the conductor in a magnetic field would cause the charge carriers to bunch on one side of the conductor and change its resistance.
    If you increase the frequency, then the self-generated field will cause the conducting electrons to concentrate towards the outer diameter and increase the effective resistance. This effect is taken into consideration in the design of long-distance transmission lines.


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  4. #3  
    Forum Freshman ScubaDiver's Avatar
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    Ok, makes sense. What you are referring to is called the "skin effect". I know quite a bit about that actually.

    So, like you said, if one creates a high frequency current on a conductor J (current density) goes up around the outside of the conductor, which increases the effective resistance.

    That's what I was getting at with the hall effect. If the conductor is situated in a magnetic field this will modify J in the conductor and thus change the effective DC resistance.
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  5. #4  
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    Resistance is an inheirent property of the material and from your list only temperatue has an effect
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  6. #5  
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    No, Resistivity is an inherent property of a material.

    Resistance is different from resistivity.

    One could make several conductors that all have the same resistivity but different resistances.
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  7. #6  
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    :I stand corrected-anyway it is temp dependent
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  8. #7  
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    Quote Originally Posted by ScubaDiver
    No, Resistivity is an inherent property of a material.

    Resistance is different from resistivity.

    One could make several conductors that all have the same resistivity but different resistances.
    Right.

    Other thought. Piezoresistive materials vary resistance with stress.

    http://en.wikipedia.org/wiki/Piezoresistive_effect
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  9. #8  
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    Don't know if this counts, as its a radical change.

    Dope the crystal structure of the resistive material so that electrons or holes are in the semi-conduction band ( higher than the valence band ) and are free to move.
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