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    Hi,
    Can anyone explain and answer this question for me please,
    thanks.

    Your given a wire (Y) Carrying a current I (see attached picture)
    Your then told that a parrallel wire (Z) is placed 12cm away from wire carrying a current of 2I . We are also given the direction of the force (Fz) on wire Z. From this we have to work out the direction of the current in Wire Z, the direction of the force acting on wire Y and the ratio of the two forces.

    Any help would be appreciated.
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    between two long wires,when their direction is opposite the force is repultion and the ratio is 1:1
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    (Original post by habosh)
    between two long wires,when their direction is opposite the force is repultion and the ratio is 1:1
    Thanks but I don't understand why the ratio is 1:1, if force is calculated by F= BIL and the current in one is twice the current in the other shouldn't the ratio be 2:1 :confused:
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    ITs from newtons 3rd law i think the force on one thing is equal and opposite on the other thing therefore the ratio must be 1:1
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    Fz = BIL
    Z is in a field of - mu0I/2pir created by Y
    Fy = BIL
    Y is in a field of - mu0I/2pir created by Z
    Twice the current means that Y is in twice the magnetic field but since it only carries half the current the force on it is a half giving 1-1.
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    Fz = BIL where I = 2I
    Fz = 2BIL
    B = muoI/2pir
    Therefore Fz = 2mu0I^2/2pir
    Fy = BIL where I = I
    B = mu0(2I)/2pir
    Therefore Fy = 2mu0I^2/2pir
    Fy = Fz
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    (Original post by Economist)
    Fz = BIL where I = 2I
    Fz = 2BIL
    B = muoI/2pir
    Therefore Fz = 2mu0I^2/2pir
    Fy = BIL where I = I
    B = mu0(2I)/2pir
    Therefore Fy = 2mu0I^2/2pir
    Fy = Fz
    Oh thanks alot that makes sense, it was a one mark question, apparently its blindingly obvious but never mind. Thanks
 
 
 
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