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gudeapp
gudeapp
Student
College - Freshman

An electrical current is going through a circular coil. The coil is input partially in a region with magnetic field.

1) Calculate the electromagnetic force which is acting on coil.

2) If the coil would be input totally in the magnetic field, which is the elastic tension from the coil?

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Posted by gudeapp on Saturday July 4, 2009 at 5:59 AM and tagged with circular coil, electrical current, magnetic field, science.

Answers:

  1. giorgiana1976
    giorgiana1976 Teacher
    Doctorate

    eNotes Editor

    Best answer as selected by question asker.

    1) We'll take an element of coil, ds=R*d tetha. The elementary force is acting on the element, this force being radially oriented:

    dF=I*dr x B, module(dr)=ds, where  

    r and B are vectors

    For each and every element ds, does exist an element, symmetrically from the axis of symmetry OX, so that the components perpendicular to the ox axis are cancelling each other. We'll consider only ox components:

    F= Integral (dF* cos tetha)=Integral (I*ds*B*cos tetha)=

    =Integral( IRBcos tetha d tetha)=2IRB Integral(cos tetha*dtetha)=2IRB*sin tetha

    For a semi-coil, tetha=pi/2, F=2IRB

    2) The result of the two tensions which are acting at the ends of the element ds, must balance the electromagnetic force dF, which is acting on the power element.

    2T sin (dtetha/2)=2T(d tetha/2)=T d tetha

    sin x tends towards to x, when x tends towards to 0.

    T d tetha=dF=IdsB=IR(d tetha)B

    T=IRB

     

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    Posted by giorgiana1976 on Tuesday July 21, 2009 at 10:41 AM