Del in cylindrical and spherical coordinates
{{Short description|Mathematical gradient operator in certain coordinate systems}}
This is a list of some vector calculus formulae for working with common curvilinear coordinate systems.
Notes
- This article uses the standard notation ISO 80000-2, which supersedes ISO 31-11, for spherical coordinates (other sources may reverse the definitions of θ and φ):
- The polar angle is denoted by : it is the angle between the z-axis and the radial vector connecting the origin to the point in question.
- The azimuthal angle is denoted by : it is the angle between the x-axis and the projection of the radial vector onto the xy-plane.
- The function {{nowrap|atan2(y, x)}} can be used instead of the mathematical function {{nowrap|arctan(y/x)}} owing to its domain and image. The classical arctan function has an image of {{nowrap|(−π/2, +π/2)}}, whereas atan2 is defined to have an image of {{nowrap|(−π, π]}}.
Coordinate conversions
class="wikitable"
|+ Conversion between Cartesian, cylindrical, and spherical coordinates{{Cite book|title=Introduction to Electrodynamics|last=Griffiths|first=David J.|publisher=Pearson|year=2012|isbn=978-0-321-85656-2}} ! colspan="2" rowspan="2" | ! colspan="3" | From |
Cartesian
! Cylindrical ! Spherical |
---|
rowspan="3" |To
! Cartesian | x&=x\\ y&=y\\ z&=z\\ \end{align} | x &= \rho \cos\varphi \\ y &= \rho \sin\varphi \\ z &= z \end{align} | x &= r \sin\theta \cos\varphi \\ y &= r \sin\theta \sin\varphi \\ z &= r \cos\theta \\ \end{align} |
Cylindrical
| \rho &= \sqrt{x^2 + y^2} \\ \varphi &= \arctan\left(\frac{y}{x}\right) \\ z &= z \end{align} | \rho &=\rho\\ \varphi &=\varphi\\ z&=z\\ \end{align} | \rho &= r \sin\theta \\ \varphi &= \varphi \\ z &= r\cos\theta \end{align} |
Spherical
| r &= \sqrt{x^2 + y^2 + z^2} \\ \theta &= \arctan\left(\frac{\sqrt{x^2 + y^2}}{z}\right) \\ \varphi &= \arctan\left(\frac{y}{x}\right) \end{align} | r &= \sqrt{\rho^2 + z^2} \\ \theta &= \arctan{\left(\frac{\rho}{z}\right)} \\ \varphi &= \varphi \end{align} | r&=r\\\theta &=\theta \\\varphi &=\varphi \end{align} |
Note that the operation must be interpreted as the two-argument inverse tangent, atan2.
Unit vector conversions
class="wikitable"
|+ Conversion between unit vectors in Cartesian, cylindrical, and spherical coordinate systems in terms of source coordinates |
! Cartesian
! Cylindrical ! Spherical |
---|
Cartesian
| \hat{\mathbf x}&=\hat{\mathbf x}\\ \hat{\mathbf y}&=\hat{\mathbf y}\\ \hat{\mathbf z}&=\hat{\mathbf z}\\ \end{align} | \hat{\mathbf x} &= \frac{x \hat{\boldsymbol \rho} - y \hat{\boldsymbol \varphi}}{\sqrt{x^2 + y^2}} \\ \hat{\mathbf y} &= \frac{y \hat{\boldsymbol \rho} + x \hat{\boldsymbol \varphi}}{\sqrt{x^2 + y^2}} \\ \hat{\mathbf z} &= \hat{\mathbf z} \end{align} | \hat{\mathbf x} &= \frac{x \left(\sqrt{x^2 + y^2} \hat{\mathbf r} + z \hat{\boldsymbol \theta}\right) - y \sqrt{x^2 + y^2 + z^2} \hat{\boldsymbol \varphi}}{\sqrt{x^2 + y^2} \sqrt{x^2 + y^2 + z^2}} \\ \hat{\mathbf y} &= \frac{y \left(\sqrt{x^2 + y^2} \hat{\mathbf r} + z \hat{\boldsymbol \theta}\right) + x \sqrt{x^2 + y^2 + z^2} \hat{\boldsymbol \varphi}}{\sqrt{x^2 + y^2} \sqrt{x^2 + y^2 + z^2}} \\ \hat{\mathbf z} &= \frac{z \hat{\mathbf r} - \sqrt{x^2 + y^2} \hat{\boldsymbol \theta}}{\sqrt{x^2 + y^2 + z^2}} \end{align} |
Cylindrical
| \hat{\boldsymbol \rho} &= \cos\varphi \hat{\mathbf x} + \sin\varphi \hat{\mathbf y} \\ \hat{\boldsymbol \varphi} &= -\sin\varphi \hat{\mathbf x} + \cos\varphi \hat{\mathbf y} \\ \hat{\mathbf z} &= \hat{\mathbf z} \end{align} | \hat{\boldsymbol \rho}&=\hat{\boldsymbol \rho}\\ \hat{\boldsymbol \varphi}&=\hat{\boldsymbol \varphi}\\ \hat{\mathbf z}&=\hat{\mathbf z}\\ \end{align} | \hat{\boldsymbol \rho} &= \frac{\rho \hat{\mathbf r} + z \hat{\boldsymbol \theta}}{\sqrt{\rho^2 + z^2}} \\ \hat{\boldsymbol \varphi} &= \hat{\boldsymbol \varphi} \\ \hat{\mathbf z} &= \frac{z \hat{\mathbf r} - \rho \hat{\boldsymbol \theta}}{\sqrt{\rho^2 + z^2}} \end{align} |
Spherical
| \hat{\mathbf r} &= \sin\theta \left(\cos\varphi \hat{\mathbf x} + \sin\varphi \hat{\mathbf y}\right) + \cos\theta \hat{\mathbf z} \\ \hat{\boldsymbol \theta} &= \cos\theta \left(\cos\varphi \hat{\mathbf x} + \sin\varphi \hat{\mathbf y}\right) - \sin\theta \hat{\mathbf z} \\ \hat{\boldsymbol \varphi} &= -\sin\varphi \hat{\mathbf x} + \cos\varphi \hat{\mathbf y} \end{align} | \hat{\mathbf r} &= \sin\theta \hat{\boldsymbol \rho} + \cos\theta \hat{\mathbf z} \\ \hat{\boldsymbol \theta} &= \cos\theta \hat{\boldsymbol \rho} - \sin\theta \hat{\mathbf z} \\ \hat{\boldsymbol \varphi} &= \hat{\boldsymbol \varphi} \end{align} | \hat{\mathbf r}&=\hat{\mathbf r}\\ \hat{\boldsymbol \theta}&=\hat{\boldsymbol \theta}\\ \hat{\boldsymbol \varphi}&=\hat{\boldsymbol \varphi}\\ \end{align} |
Del formula
class="wikitable" style="text-align: center;"
|+ Table with the del operator in cartesian, cylindrical and spherical coordinates |
Operation
! Cartesian coordinates {{math|(x, y, z)}} ! Cylindrical coordinates {{math|(ρ, φ, z)}} ! Spherical coordinates {{math|(r, θ, φ)}}, |
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Vector field {{math|A}}
| | | |
Gradient {{math|∇f}}
| + {\partial f \over \partial z}\hat{\mathbf z} | + {1 \over \rho}{\partial f \over \partial \varphi}\hat{\boldsymbol \varphi} + {\partial f \over \partial z}\hat{\mathbf z} | + {1 \over r}{\partial f \over \partial \theta}\hat{\boldsymbol \theta} + {1 \over r\sin\theta}{\partial f \over \partial \varphi}\hat{\boldsymbol \varphi} |
Divergence {{math|∇ ⋅ A}}
| | + {1 \over \rho}{\partial A_\varphi \over \partial \varphi} + {\partial A_z \over \partial z} | + {1 \over r\sin\theta}{\partial \over \partial \theta} \left( A_\theta\sin\theta \right) + {1 \over r\sin\theta}{\partial A_\varphi \over \partial \varphi} |
Curl {{math|∇ × A}}
| \left(\frac{\partial A_z}{\partial y} - \frac{\partial A_y}{\partial z}\right) &\hat{\mathbf x} \\ + \left(\frac{\partial A_x}{\partial z} - \frac{\partial A_z}{\partial x}\right) &\hat{\mathbf y} \\ + \left(\frac{\partial A_y}{\partial x} - \frac{\partial A_x}{\partial y}\right) &\hat{\mathbf z} \end{align} | \left( \frac{1}{\rho}\frac{\partial A_z}{\partial \varphi} - \frac{\partial A_\varphi}{\partial z} \right) &\hat{\boldsymbol \rho} \\ + \left( \frac{\partial A_\rho}{\partial z} - \frac{\partial A_z}{\partial \rho} \right) &\hat{\boldsymbol \varphi} \\ + \frac{1}{\rho} \left( \frac{\partial \left(\rho A_\varphi\right)}{\partial \rho} - \frac{\partial A_\rho}{\partial \varphi} \right) &\hat{\mathbf z} \end{align} | \frac{1}{r\sin\theta} \left( \frac{\partial}{\partial \theta} \left(A_\varphi\sin\theta \right) - \frac{\partial A_\theta}{\partial \varphi} \right) &\hat{\mathbf r} \\ {}+ \frac{1}{r} \left( \frac{1}{\sin\theta} \frac{\partial A_r}{\partial \varphi} - \frac{\partial}{\partial r} \left( r A_\varphi \right) \right) &\hat{\boldsymbol \theta} \\ {}+ \frac{1}{r} \left( \frac{\partial}{\partial r} \left( r A_{\theta} \right) - \frac{\partial A_r}{\partial \theta} \right) &\hat{\boldsymbol \varphi} \end{align} |
Laplace operator {{math|∇2f ≡ ∆f}}
| | + {1 \over \rho^2}{\partial^2 f \over \partial \varphi^2} + {\partial^2 f \over \partial z^2} | \!+\!{1 \over r^2\!\sin\theta}{\partial \over \partial \theta}\!\left(\sin\theta {\partial f \over \partial \theta}\right) \!+\!{1 \over r^2\!\sin^2\theta}{\partial^2 f \over \partial \varphi^2} |
Vector gradient {{math|∇A}}{{ref|Beta|β}}
| | | |
Vector Laplacian {{math|∇2A ≡ ∆A}}{{cite book |last1=Arfken |first1=George |last2=Weber |first2=Hans |last3=Harris |first3=Frank |title=Mathematical Methods for Physicists |date=2012 |publisher=Academic Press |isbn=9789381269558 |page=192 |edition=Seventh |ref=arfkenweber}}
| | \mathopen{}\left(\nabla^2 A_\rho - \frac{A_\rho}{\rho^2} - \frac{2}{\rho^2} \frac{\partial A_\varphi}{\partial \varphi}\right)\mathclose{} &\hat{\boldsymbol \rho} \\ + \mathopen{}\left(\nabla^2 A_\varphi - \frac{A_\varphi}{\rho^2} + \frac{2}{\rho^2} \frac{\partial A_\rho}{\partial \varphi}\right)\mathclose{} &\hat{\boldsymbol \varphi} \\ {}+ \nabla^2 A_z &\hat{\mathbf z} \end{align} | \left(\nabla^2 A_r - \frac{2 A_r}{r^2} - \frac{2}{r^2\sin\theta} \frac{\partial \left(A_\theta \sin\theta\right)}{\partial\theta} - \frac{2}{r^2\sin\theta}{\frac{\partial A_\varphi}{\partial \varphi}}\right) &\hat{\mathbf r} \\ + \left(\nabla^2 A_\theta - \frac{A_\theta}{r^2\sin^2\theta} + \frac{2}{r^2} \frac{\partial A_r}{\partial \theta} - \frac{2 \cos\theta}{r^2\sin^2\theta} \frac{\partial A_\varphi}{\partial \varphi}\right) &\hat{\boldsymbol \theta} \\ + \left(\nabla^2 A_\varphi - \frac{A_\varphi}{r^2\sin^2\theta} + \frac{2}{r^2\sin\theta} \frac{\partial A_r}{\partial \varphi} + \frac{2 \cos\theta}{r^2\sin^2\theta} \frac{\partial A_\theta}{\partial \varphi}\right) &\hat{\boldsymbol \varphi} \end{align} |
Directional derivative {{math|(A ⋅ ∇)B}}{{cite web |url=http://mathworld.wolfram.com/ConvectiveOperator.html|title=Convective Operator |author=Weisstein, Eric W. |work=Mathworld |access-date=23 March 2011}}
| | \left(A_\rho \frac{\partial B_\rho}{\partial \rho}+\frac{A_\varphi}{\rho}\frac{\partial B_\rho}{\partial \varphi}+A_z\frac{\partial B_\rho}{\partial z}-\frac{A_\varphi B_\varphi}{\rho}\right) &\hat{\boldsymbol \rho} \\ + \left(A_\rho \frac{\partial B_\varphi}{\partial \rho} + \frac{A_\varphi}{\rho}\frac{\partial B_\varphi}{\partial \varphi} + A_z\frac{\partial B_\varphi}{\partial z} + \frac{A_\varphi B_\rho}{\rho}\right) &\hat{\boldsymbol \varphi}\\ + \left(A_\rho \frac{\partial B_z}{\partial \rho}+\frac{A_\varphi}{\rho}\frac{\partial B_z}{\partial \varphi}+A_z\frac{\partial B_z}{\partial z}\right) &\hat{\mathbf z} \end{align} | \left( A_r \frac{\partial B_r}{\partial r} + \frac{A_\theta}{r} \frac{\partial B_r}{\partial \theta} + \frac{A_\varphi}{r\sin\theta} \frac{\partial B_r}{\partial \varphi} - \frac{A_\theta B_\theta + A_\varphi B_\varphi}{r} \right) &\hat{\mathbf r} \\ + \left( A_r \frac{\partial B_\theta}{\partial r} + \frac{A_\theta}{r} \frac{\partial B_\theta}{\partial \theta} + \frac{A_\varphi}{r\sin\theta} \frac{\partial B_\theta}{\partial \varphi} + \frac{A_\theta B_r}{r} - \frac{A_\varphi B_\varphi\cot\theta}{r} \right) &\hat{\boldsymbol \theta} \\ + \left( A_r \frac{\partial B_\varphi}{\partial r} + \frac{A_\theta}{r} \frac{\partial B_\varphi}{\partial \theta} + \frac{A_\varphi}{r\sin\theta} \frac{\partial B_\varphi}{\partial \varphi} + \frac{A_\varphi B_r}{r} + \frac{A_\varphi B_\theta \cot\theta}{r} \right) &\hat{\boldsymbol \varphi} \end{align} |
Tensor divergence {{math|∇ ⋅ T}}{{ref|Gamma|γ}}
| \left(\frac{\partial T_{xx}}{\partial x}+\frac{\partial T_{yx}}{\partial y}+\frac{\partial T_{zx}}{\partial z}\right)&\hat{\mathbf x} \\ +\left(\frac{\partial T_{xy}}{\partial x}+\frac{\partial T_{yy}}{\partial y}+\frac{\partial T_{zy}}{\partial z}\right)&\hat{\mathbf y} \\ +\left(\frac{\partial T_{xz}}{\partial x}+\frac{\partial T_{yz}}{\partial y}+\frac{\partial T_{zz}}{\partial z}\right)&\hat{\mathbf z} \end{align} | \left[\frac{\partial T_{\rho\rho}}{\partial\rho}+\frac1\rho\frac{\partial T_{\varphi\rho}}{\partial\varphi}+\frac{\partial T_{z\rho}}{\partial z}+\frac1\rho(T_{\rho\rho}-T_{\varphi\varphi})\right]&\hat{\boldsymbol\rho} \\ +\left[\frac{\partial T_{\rho\varphi}}{\partial\rho}+\frac1\rho\frac{\partial T_{\varphi\varphi}}{\partial\varphi}+\frac{\partial T_{z\varphi}}{\partial z}+\frac1\rho(T_{\rho\varphi}+T_{\varphi\rho})\right]&\hat{\boldsymbol\varphi} \\ +\left[\frac{\partial T_{\rho z}}{\partial\rho}+\frac1\rho\frac{\partial T_{\varphi z}}{\partial\varphi}+\frac{\partial T_{zz}}{\partial z}+\frac{T_{\rho z}}\rho\right]&\hat{\mathbf z} \end{align} | \left[\frac{\partial T_{rr}}{\partial r}+2\frac{T_{rr}}r+\frac1r\frac{\partial T_{\theta r}}{\partial\theta}+\frac{\cot\theta}rT_{\theta r}+\frac1{r\sin\theta}\frac{\partial T_{\varphi r}}{\partial\varphi}-\frac1r(T_{\theta\theta}+T_{\varphi\varphi})\right]&\hat{\mathbf r} \\ +\left[\frac{\partial T_{r\theta}}{\partial r}+2\frac{T_{r\theta}}r+\frac1r\frac{\partial T_{\theta\theta}}{\partial\theta}+\frac{\cot\theta}rT_{\theta\theta}+\frac1{r\sin\theta}\frac{\partial T_{\varphi\theta}}{\partial\varphi}+\frac{T_{\theta r}}r-\frac{\cot\theta}rT_{\varphi\varphi}\right]&\hat{\boldsymbol\theta} \\ +\left[\frac{\partial T_{r\varphi}}{\partial r}+2\frac{T_{r\varphi}}r+\frac1r\frac{\partial T_{\theta\varphi}}{\partial\theta}+\frac1{r\sin\theta}\frac{\partial T_{\varphi\varphi}}{\partial\varphi}+\frac {T_{\varphi r}}{r}+\frac{\cot\theta}{r} (T_{\theta\varphi}+T_{\varphi\theta})\right]&\hat{\boldsymbol\varphi} \end{align} |
Differential displacement {{math|dℓ}}
| | | |
Differential normal area {{math|dS}}
| dy \, dz &\, \hat{\mathbf x} \\ {} + dx \, dz &\, \hat{\mathbf y} \\ {} + dx \, dy &\, \hat{\mathbf z} \end{align} | \rho \, d\varphi \, dz &\, \hat{\boldsymbol \rho} \\ {} + d\rho \, dz &\, \hat{\boldsymbol \varphi} \\ {} + \rho \, d\rho \, d\varphi &\, \hat{\mathbf z} \end{align} | r^2 \sin\theta \, d\theta \, d\varphi &\, \hat{\mathbf r} \\ {} + r \sin\theta \, dr \, d\varphi &\, \hat{\boldsymbol \theta} \\ {} + r \, dr \, d\theta &\, \hat{\boldsymbol \varphi} \end{align} |
Differential volume {{math|dV}}
| | | |
:{{note|Alpha|α}} This page uses for the polar angle and for the azimuthal angle, which is common notation in physics. The source that is used for these formulae uses for the azimuthal angle and for the polar angle, which is common mathematical notation. In order to get the mathematics formulae, switch and in the formulae shown in the table above.
:{{note|Beta|β}} Defined in Cartesian coordinates as . An alternative definition is .
:{{note|Gamma|γ}} Defined in Cartesian coordinates as . An alternative definition is .
= Calculation rules =
- (Lagrange's formula for del)
- (From {{cite journal | last=Fernández-Guasti | first=M. | title=Green's Second Identity for Vector Fields | journal=ISRN Mathematical Physics | publisher=Hindawi Limited | volume=2012 | year=2012 | issn=2090-4681 | doi=10.5402/2012/973968 | pages=1–7| doi-access=free }} )
Cartesian derivation
\operatorname{div} \mathbf A = \lim_{V\to 0} \frac{\iint_{\partial V} \mathbf A \cdot d\mathbf{S}}{\iiint_V dV}
&= \frac{A_x(x+dx)\,dy\,dz - A_x(x)\,dy\,dz + A_y(y+dy)\,dx\,dz - A_y(y)\,dx\,dz + A_z(z+dz)\,dx\,dy - A_z(z)\,dx\,dy}{dx\,dy\,dz} \\
&= \frac{\partial A_x}{\partial x} + \frac{\partial A_y}{\partial y} + \frac{\partial A_z}{\partial z}
\end{align}
(\operatorname{curl} \mathbf A)_x = \lim_{S^{\perp \mathbf{\hat x}}\to 0} \frac{\int_{\partial S} \mathbf A \cdot d\mathbf{\ell}}{\iint_{S} dS}
&= \frac{A_z(y+dy)\,dz - A_z(y)\,dz + A_y(z)\,dy - A_y(z+dz)\,dy }{dy\,dz} \\
&= \frac{\partial A_z}{\partial y} - \frac{\partial A_y}{\partial z}
\end{align}
The expressions for and are found in the same way.
Cylindrical derivation
\operatorname{div} \mathbf A &= \lim_{V\to 0} \frac{\iint_{\partial V} \mathbf A \cdot d\mathbf{S}}{\iiint_V dV} \\
&= \frac{A_\rho(\rho+d\rho)(\rho+d\rho)\,d\phi\, dz - A_\rho(\rho)\rho \,d\phi \,dz + A_\phi(\phi+d\phi)\,d\rho\, dz - A_\phi(\phi)\,d\rho\, dz + A_z(z+dz)\,d\rho\, (\rho +d\rho/2)\,d\phi - A_z(z)\,d\rho (\rho +d\rho/2)\, d\phi}{\rho \,d\phi \,d\rho\, dz} \\
&= \frac 1 \rho \frac{\partial (\rho A_\rho)}{\partial \rho} + \frac 1 \rho \frac{\partial A_\phi}{\partial \phi} + \frac{\partial A_z}{\partial z}
\end{align}
(\operatorname{curl} \mathbf A)_\rho
&= \lim_{S^{\perp \hat{\boldsymbol \rho}}\to 0} \frac{\int_{\partial S} \mathbf A \cdot d\boldsymbol{\ell}}{\iint_{S} dS} \\[1ex]
&= \frac{A_\phi (z) \left(\rho+d\rho\right)\,d\phi - A_\phi(z+dz) \left(\rho+d\rho\right)\,d\phi + A_z(\phi + d\phi)\,dz - A_z(\phi)\,dz}{\left(\rho+d\rho\right)\,d\phi \,dz} \\[1ex]
&= -\frac{\partial A_\phi}{\partial z} + \frac{1}{\rho} \frac{\partial A_z}{\partial \phi}
\end{align}
(\operatorname{curl} \mathbf A)_\phi &= \lim_{S^{\perp \boldsymbol{\hat \phi}}\to 0} \frac{\int_{\partial S} \mathbf A \cdot d\boldsymbol{\ell}}{\iint_{S} dS} \\
&= \frac{A_z (\rho)\,dz - A_z(\rho + d\rho)\,dz + A_\rho(z+dz)\,d\rho - A_\rho(z)\,d\rho}{d\rho \,dz} \\
&= -\frac{\partial A_z}{\partial \rho} + \frac{\partial A_\rho}{\partial z}
\end{align}
(\operatorname{curl} \mathbf A)_z &= \lim_{S^{\perp \hat{\boldsymbol z}}\to 0} \frac{\int_{\partial S} \mathbf A \cdot d\mathbf{\ell}}{\iint_{S} dS} \\[1ex]
&= \frac{A_\rho(\phi)\,d\rho - A_\rho(\phi + d\phi)\,d\rho + A_\phi(\rho + d\rho)(\rho + d\rho)\,d\phi - A_\phi(\rho)\rho \,d\phi}{\rho \,d\rho \,d\phi} \\[1ex]
&= -\frac{1}{\rho}\frac{\partial A_\rho}{\partial \phi} + \frac{1}{\rho} \frac{\partial (\rho A_\phi)}{\partial \rho}
\end{align}
\operatorname{curl} \mathbf A &= (\operatorname{curl} \mathbf A)_\rho \hat{\boldsymbol \rho} + (\operatorname{curl} \mathbf A)_\phi \hat{\boldsymbol \phi} + (\operatorname{curl} \mathbf A)_z \hat{\boldsymbol z} \\[1ex]
&= \left(\frac{1}{\rho} \frac{\partial A_z}{\partial \phi} -\frac{\partial A_\phi}{\partial z} \right) \hat{\boldsymbol \rho} + \left(\frac{\partial A_\rho}{\partial z}-\frac{\partial A_z}{\partial \rho} \right) \hat{\boldsymbol \phi} + \frac{1}{\rho}\left(\frac{\partial (\rho A_\phi)}{\partial \rho} - \frac{\partial A_\rho}{\partial \phi} \right) \hat{\boldsymbol z}
\end{align}
Spherical derivation
\operatorname{div} \mathbf A &= \lim_{V\to 0} \frac{\iint_{\partial V} \mathbf A \cdot d\mathbf{S}}{\iiint_V dV} \\
&= \frac{A_r(r+dr)(r+dr)\,d\theta\, (r+dr)\sin\theta \,d\phi - A_r(r)r\,d\theta\, r\sin\theta \,d\phi + A_\theta(\theta+d\theta)\sin(\theta + d\theta)r\, dr\, d\phi - A_\theta(\theta)\sin(\theta)r \,dr \,d\phi + A_\phi(\phi + d\phi)r\,dr\, d\theta - A_\phi(\phi)r\,dr \,d\theta}{dr\,r\,d\theta\,r\sin\theta\, d\phi} \\
&= \frac{1}{r^2}\frac{\partial (r^2A_r)}{\partial r} + \frac{1}{r \sin\theta} \frac{\partial(A_\theta\sin\theta)}{\partial \theta} + \frac{1}{r \sin\theta} \frac{\partial A_\phi}{\partial \phi}
\end{align}
(\operatorname{curl} \mathbf A)_r = \lim_{S^{\perp \boldsymbol{\hat r}}\to 0} \frac{\int_{\partial S} \mathbf A \cdot d\mathbf{\ell}}{\iint_{S} dS}
&= \frac{A_\theta(\phi)r \,d\theta + A_\phi(\theta + d\theta)r \sin(\theta + d\theta)\, d\phi
- A_\theta(\phi + d\phi)r \,d\theta - A_\phi(\theta)r\sin(\theta)\, d\phi}{r\, d\theta\,r\sin\theta \,d\phi} \\
&= \frac{1}{r\sin\theta}\frac{\partial(A_\phi \sin\theta)}{\partial \theta}
- \frac{1}{r\sin\theta} \frac{\partial A_\theta}{\partial \phi}
\end{align}
(\operatorname{curl} \mathbf A)_\theta = \lim_{S^{\perp \boldsymbol{\hat \theta}}\to 0} \frac{\int_{\partial S} \mathbf A \cdot d\mathbf{\ell}}{\iint_{S} dS}
&= \frac{A_\phi(r)r \sin\theta \,d\phi + A_r(\phi + d\phi)\,dr
- A_\phi(r+dr)(r+dr)\sin\theta \,d\phi - A_r(\phi)\,dr}{dr \, r \sin \theta \,d\phi} \\
&= \frac{1}{r\sin\theta}\frac{\partial A_r}{\partial \phi}
- \frac{1}{r} \frac{\partial (rA_\phi)}{\partial r}
\end{align}
(\operatorname{curl} \mathbf A)_\phi = \lim_{S^{\perp \boldsymbol{\hat \phi}}\to 0} \frac{\int_{\partial S} \mathbf A \cdot d\mathbf{\ell}}{\iint_{S} dS}
&= \frac{A_r(\theta)\,dr + A_\theta(r+dr)(r+dr)\,d\theta
- A_r(\theta+d\theta)\,dr - A_\theta(r) r \,d\theta}{r\,dr\, d\theta} \\
&= \frac{1}{r}\frac{\partial(rA_\theta)}{\partial r}
- \frac{1}{r} \frac{\partial A_r}{\partial \theta}
\end{align}
\operatorname{curl} \mathbf A
&= (\operatorname{curl} \mathbf A)_r \, \hat{\boldsymbol r} + (\operatorname{curl} \mathbf A)_\theta \, \hat{\boldsymbol \theta} + (\operatorname{curl} \mathbf A)_\phi \, \hat{\boldsymbol \phi} \\[1ex]
&= \frac{1}{r\sin\theta} \left(\frac{\partial(A_\phi \sin\theta)}{\partial \theta}-\frac{\partial A_\theta}{\partial \phi} \right) \hat{\boldsymbol r} +\frac{1}{r} \left(\frac{1}{\sin\theta}\frac{\partial A_r}{\partial \phi} - \frac{\partial (rA_\phi)}{\partial r} \right) \hat{\boldsymbol \theta} + \frac{1}{r}\left(\frac{\partial(rA_\theta)}{\partial r} - \frac{\partial A_r}{\partial \theta} \right) \hat{\boldsymbol \phi}
\end{align}
Unit vector conversion formula
The unit vector of a coordinate parameter u is defined in such a way that a small positive change in u causes the position vector to change in direction.
Therefore,
where {{mvar|s}} is the arc length parameter.
For two sets of coordinate systems and , according to chain rule,
Now, we isolate the th component. For , let . Then divide on both sides by to get:
See also
References
{{Reflist}}
External links
- [http://www.csulb.edu/~woollett/ Maxima Computer Algebra system scripts] to generate some of these operators in cylindrical and spherical coordinates.