What is the proof for the Vortex vector field equation?











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I'm Struggling to understand why the vortex vector field is given by:



Vortex vector field equation



$vec F(x,y) = (frac{-y}{x^2+y^2}, frac{x}{x^2+y^2})$



If anyone could explain why this is, I would be very grateful.



Thank you.










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    up vote
    4
    down vote

    favorite












    I'm Struggling to understand why the vortex vector field is given by:



    Vortex vector field equation



    $vec F(x,y) = (frac{-y}{x^2+y^2}, frac{x}{x^2+y^2})$



    If anyone could explain why this is, I would be very grateful.



    Thank you.










    share|cite|improve this question


























      up vote
      4
      down vote

      favorite









      up vote
      4
      down vote

      favorite











      I'm Struggling to understand why the vortex vector field is given by:



      Vortex vector field equation



      $vec F(x,y) = (frac{-y}{x^2+y^2}, frac{x}{x^2+y^2})$



      If anyone could explain why this is, I would be very grateful.



      Thank you.










      share|cite|improve this question















      I'm Struggling to understand why the vortex vector field is given by:



      Vortex vector field equation



      $vec F(x,y) = (frac{-y}{x^2+y^2}, frac{x}{x^2+y^2})$



      If anyone could explain why this is, I would be very grateful.



      Thank you.







      multivariable-calculus vectors vector-analysis






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      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Nov 18 at 1:25









      Mark Viola

      129k1273170




      129k1273170










      asked Nov 18 at 0:03









      Will Righton

      264




      264






















          1 Answer
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          down vote



          accepted










          For $vec F=-hat x frac {y}{x^2+y^2} +hat y frac{x}{x^2+y^2}$, we see that



          $$|vec F|=frac1r$$



          where $r=sqrt{x^2+y^2}$ is the polar coordinate for the magnitude of the position vector $vec r=hat r r$.



          Moreover, the direction of $vec v$ is the polar unit vector $hat theta$ and is perpendicular to the position vector.



          Hence, $vec F$ rotates (circulates) around the origin counterclockwise and its "strength" increases as we move closer to the origin.



          A point of interest is that while $nabla times vec F=0$ for all $vec rne0$, the line integral of $vec F$ is not $0$ for any (smooth) contour that encircles the origin.






          share|cite|improve this answer























          • Would the cowardly down voter care to comment?
            – Mark Viola
            Nov 18 at 2:22










          • Hi mark, thanks for your reply! Why is the direction of F perpendicular to the position vector r
            – Will Righton
            Nov 18 at 10:33






          • 1




            @WillRighton: Because $vec{F} cdot vec{r} = 0$, since $vec{r} = (x , y)$ in Cartesian coordinates.
            – Nominal Animal
            Nov 18 at 13:58










          • @willrighton Hi Will. You're welcome. My pleasure. And it appears that your question was answered in another comment.
            – Mark Viola
            Nov 18 at 14:39











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          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes








          up vote
          1
          down vote



          accepted










          For $vec F=-hat x frac {y}{x^2+y^2} +hat y frac{x}{x^2+y^2}$, we see that



          $$|vec F|=frac1r$$



          where $r=sqrt{x^2+y^2}$ is the polar coordinate for the magnitude of the position vector $vec r=hat r r$.



          Moreover, the direction of $vec v$ is the polar unit vector $hat theta$ and is perpendicular to the position vector.



          Hence, $vec F$ rotates (circulates) around the origin counterclockwise and its "strength" increases as we move closer to the origin.



          A point of interest is that while $nabla times vec F=0$ for all $vec rne0$, the line integral of $vec F$ is not $0$ for any (smooth) contour that encircles the origin.






          share|cite|improve this answer























          • Would the cowardly down voter care to comment?
            – Mark Viola
            Nov 18 at 2:22










          • Hi mark, thanks for your reply! Why is the direction of F perpendicular to the position vector r
            – Will Righton
            Nov 18 at 10:33






          • 1




            @WillRighton: Because $vec{F} cdot vec{r} = 0$, since $vec{r} = (x , y)$ in Cartesian coordinates.
            – Nominal Animal
            Nov 18 at 13:58










          • @willrighton Hi Will. You're welcome. My pleasure. And it appears that your question was answered in another comment.
            – Mark Viola
            Nov 18 at 14:39















          up vote
          1
          down vote



          accepted










          For $vec F=-hat x frac {y}{x^2+y^2} +hat y frac{x}{x^2+y^2}$, we see that



          $$|vec F|=frac1r$$



          where $r=sqrt{x^2+y^2}$ is the polar coordinate for the magnitude of the position vector $vec r=hat r r$.



          Moreover, the direction of $vec v$ is the polar unit vector $hat theta$ and is perpendicular to the position vector.



          Hence, $vec F$ rotates (circulates) around the origin counterclockwise and its "strength" increases as we move closer to the origin.



          A point of interest is that while $nabla times vec F=0$ for all $vec rne0$, the line integral of $vec F$ is not $0$ for any (smooth) contour that encircles the origin.






          share|cite|improve this answer























          • Would the cowardly down voter care to comment?
            – Mark Viola
            Nov 18 at 2:22










          • Hi mark, thanks for your reply! Why is the direction of F perpendicular to the position vector r
            – Will Righton
            Nov 18 at 10:33






          • 1




            @WillRighton: Because $vec{F} cdot vec{r} = 0$, since $vec{r} = (x , y)$ in Cartesian coordinates.
            – Nominal Animal
            Nov 18 at 13:58










          • @willrighton Hi Will. You're welcome. My pleasure. And it appears that your question was answered in another comment.
            – Mark Viola
            Nov 18 at 14:39













          up vote
          1
          down vote



          accepted







          up vote
          1
          down vote



          accepted






          For $vec F=-hat x frac {y}{x^2+y^2} +hat y frac{x}{x^2+y^2}$, we see that



          $$|vec F|=frac1r$$



          where $r=sqrt{x^2+y^2}$ is the polar coordinate for the magnitude of the position vector $vec r=hat r r$.



          Moreover, the direction of $vec v$ is the polar unit vector $hat theta$ and is perpendicular to the position vector.



          Hence, $vec F$ rotates (circulates) around the origin counterclockwise and its "strength" increases as we move closer to the origin.



          A point of interest is that while $nabla times vec F=0$ for all $vec rne0$, the line integral of $vec F$ is not $0$ for any (smooth) contour that encircles the origin.






          share|cite|improve this answer














          For $vec F=-hat x frac {y}{x^2+y^2} +hat y frac{x}{x^2+y^2}$, we see that



          $$|vec F|=frac1r$$



          where $r=sqrt{x^2+y^2}$ is the polar coordinate for the magnitude of the position vector $vec r=hat r r$.



          Moreover, the direction of $vec v$ is the polar unit vector $hat theta$ and is perpendicular to the position vector.



          Hence, $vec F$ rotates (circulates) around the origin counterclockwise and its "strength" increases as we move closer to the origin.



          A point of interest is that while $nabla times vec F=0$ for all $vec rne0$, the line integral of $vec F$ is not $0$ for any (smooth) contour that encircles the origin.







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Nov 18 at 2:34

























          answered Nov 18 at 0:25









          Mark Viola

          129k1273170




          129k1273170












          • Would the cowardly down voter care to comment?
            – Mark Viola
            Nov 18 at 2:22










          • Hi mark, thanks for your reply! Why is the direction of F perpendicular to the position vector r
            – Will Righton
            Nov 18 at 10:33






          • 1




            @WillRighton: Because $vec{F} cdot vec{r} = 0$, since $vec{r} = (x , y)$ in Cartesian coordinates.
            – Nominal Animal
            Nov 18 at 13:58










          • @willrighton Hi Will. You're welcome. My pleasure. And it appears that your question was answered in another comment.
            – Mark Viola
            Nov 18 at 14:39


















          • Would the cowardly down voter care to comment?
            – Mark Viola
            Nov 18 at 2:22










          • Hi mark, thanks for your reply! Why is the direction of F perpendicular to the position vector r
            – Will Righton
            Nov 18 at 10:33






          • 1




            @WillRighton: Because $vec{F} cdot vec{r} = 0$, since $vec{r} = (x , y)$ in Cartesian coordinates.
            – Nominal Animal
            Nov 18 at 13:58










          • @willrighton Hi Will. You're welcome. My pleasure. And it appears that your question was answered in another comment.
            – Mark Viola
            Nov 18 at 14:39
















          Would the cowardly down voter care to comment?
          – Mark Viola
          Nov 18 at 2:22




          Would the cowardly down voter care to comment?
          – Mark Viola
          Nov 18 at 2:22












          Hi mark, thanks for your reply! Why is the direction of F perpendicular to the position vector r
          – Will Righton
          Nov 18 at 10:33




          Hi mark, thanks for your reply! Why is the direction of F perpendicular to the position vector r
          – Will Righton
          Nov 18 at 10:33




          1




          1




          @WillRighton: Because $vec{F} cdot vec{r} = 0$, since $vec{r} = (x , y)$ in Cartesian coordinates.
          – Nominal Animal
          Nov 18 at 13:58




          @WillRighton: Because $vec{F} cdot vec{r} = 0$, since $vec{r} = (x , y)$ in Cartesian coordinates.
          – Nominal Animal
          Nov 18 at 13:58












          @willrighton Hi Will. You're welcome. My pleasure. And it appears that your question was answered in another comment.
          – Mark Viola
          Nov 18 at 14:39




          @willrighton Hi Will. You're welcome. My pleasure. And it appears that your question was answered in another comment.
          – Mark Viola
          Nov 18 at 14:39


















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