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Homework Statement
Sketch each of the following vector fields.
[itex]E_5 = \hat \phi r[/itex]
[itex]E_6 = \hat r \sin(\phi)[/itex]
I wish to determine the [itex]\hat x[/itex] and [itex]\hat y[/itex] components for the vector fields so that I can plot them using the quiver function in MATLAB.
Homework Equations
A cylindrical coordinate is given by [itex](r, \phi, z)[/itex]
[itex]r = \sqrt[+]{x^2 + y^2}[/itex]
[itex]\phi = \arctan(y/x)[/itex]
[itex]z = z[/itex]
Transformation from cylindrical coordinates into Cartesian coordinates:
[itex]\hat x = \hat r \cos(\phi) - \hat \phi \sin(\phi)[/itex]
[itex]\hat y = \hat r \sin(\phi) + \hat \phi \cos(\phi)[/itex]
The Attempt at a Solution
[itex]E_5 = \hat \phi r[/itex]
Since the given vector field [itex]E_5[/itex] only has a [itex]\hat \phi[/itex] component,
[itex]\hat x = \hat r \cos(\phi) - \hat \phi \sin(\phi) = 0 \cos(\phi) - r \sin(\phi) = - \sqrt[+]{x^2 + y^2} \sin(\phi)[/itex]
Then I transformed [itex]\phi[/itex] in terms of [itex]x[/itex] and [itex]y[/itex] based on the definition of a cylindrical coordinate
[itex]\hat x = - \sqrt{x^2 + y^2} \sin(\arctan(y/x)) = \displaystyle \frac{-y \sqrt{x^2 + y^2} }{x \sqrt{1 +y^2 /x^2} }[/itex]
I followed the same approach for the [itex]\hat y[/itex] component
[itex]\hat y = \hat r \sin(\phi) + \hat \phi \cos(\phi) = 0 \sin(\phi) + r \cos(\phi) = \sqrt[+]{x^2 + y^2} \cos(\phi)[/itex]
[itex]\hat y = \sqrt{x^2 + y^2} \cos(\arctan(y/x)) = \displaystyle \frac{\sqrt{x^2 + y^2} }{\sqrt{1 +y^2 /x^2} }[/itex]
Then
[itex]E_5 = - \hat x \displaystyle \frac{y \sqrt{x^2 + y^2} }{x \sqrt{1 +y^2 /x^2} } + \hat y \displaystyle \frac{\sqrt{x^2 + y^2} }{\sqrt{1 +y^2 /x^2} }[/itex]
Is this approach valid? Thanks for helping. I'll post my attempt for [itex]E_6[/itex] in a little while.
I'm having trouble thinking about the vector field since I'm used to working in Cartesian coordinates, so I can't tell if this makes sense.
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