does anybody knows how can I plot one or two vectors? (I don't want to plot the vectorial field)? My target is to plot the electric field produced by a circle on a point and show how the point moves. To reach that target I thought to use "Manipulate" to move the point. I'm at base level, so please don't be too complicate :D. That's what i want to produce: My task:


2 Answers 2


In your case, you have some arrows that are all drawn in the same style. This allows you to put all of them into a single Arrow command. For several differently colored arrows you would then have groups of Arrow commands for each different style:

 Graphics[{Black, Thick, Circle[{-x, 0}, r], PointSize[.03], 
   Point[{0, 0}],
   Line[{{{-x, r}, {0, 0}}, {{-x, -r}, {0, 0}}}],
   Arrow[{{{0, 0}, e {x, r}/Norm[{x, r}]}, {{0, 0}, 
      e {x, -r}/Norm[{x, r}]}}],
   Arrow[{e {{x, r}, {2 x, 0}}/Norm[{x, r}], 
     e {{x, -r}, {2 x, 0}}/Norm[{x, r}]}],
   Arrow[{{0, 0}, {2 e x/Norm[{x, r}], 0}}]
   }, PlotRange -> {{-3.5, 3.5}, {-1.5, 1.5}}],
 {{x, 1.5}, 1, 2}, {{r, .5}, .1, 2}, {{e, 1.6}, .3, 2}


Here, the point is at the origin, and x is the distance to the center of the circle. The arrows are given a length e, and I assume you want the brown arrow to correspond to their sum (even though the sketch in the question didn't quite draw it that way - my way makes more sense to me).

Graphics[{Arrow[{{x1,y1},{x2,y2}}], Arrow[{{x3,y3},{x4,y4}}]]

For example:

Graphics[{{Red, Arrow[{{0, 0}, {1, 3}}]}, {Green, Arrow[{{2, 6}, {4, 3}}]}}]

enter image description here


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