Pre-Quantum Electrodynamics
Cylindrical Coordinatesc.m.cs.cyl
\((r, \varphi, z)\). Relation to Cartesian coordinates:
\begin{equation} x = r \cos \varphi, y = r \sin \varphi, z = z \label{Gr(1.74)} \end{equation}The unit vectors are
\begin{equation} \hat{\bf r} = \cos \varphi ~\hat{\bf x} + \sin \varphi~\hat{\bf y}, \hspace{5mm} \hat{\boldsymbol \varphi} = -\sin \varphi ~\hat{\bf x} + \cos \varphi~\hat{\bf y}, \hat{\bf z} = \hat{\bf z}. \label{Gr(1.75)} \end{equation}Infinitesimal displacement:
\begin{equation} d{\bf l} = dr ~\hat{\bf r} + r d\varphi~\hat{\boldsymbol \varphi} + dz ~\hat{\bf z}. \label{Gr(1.77)} \end{equation}Volume element:
\begin{equation} d\tau = r dr d\varphi dz \label{Gr(1.78)} \end{equation}Range of parameters: \(r \in [0, \infty[\), \(\varphi \in [0, 2\pi[\) and \(z \in ]-\infty, \infty[\).
Curl
\begin{align}
{\boldsymbol \nabla} \times {\bf v} = \left( \frac{1}{r} \frac{\partial v_z}{\partial \varphi} - \frac{\partial v_{\varphi}}{\partial z}\right) ~\hat{\bf r}
+ \left( \frac{\partial v_r}{\partial z} - \frac{\partial v_z}{\partial r} \right) ~\hat{\boldsymbol \varphi} \nonumber \\
+ \frac{1}{r} \left( \frac{\partial}{\partial r} (r v_{\varphi}) - \frac{\partial v_r}{\partial \varphi} \right) ~\hat{\bf z}
\tag{cyl_curl}
\label{cyl_curl}
\end{align}
Laplacian
\begin{equation}
{\boldsymbol \nabla}^2 T = \frac{1}{r} \frac{\partial}{\partial r} \left( r \frac{\partial T}{\partial r} \right)
+ \frac{1}{r^2} \frac{\partial^2 T}{\partial \varphi^2} + \frac{\partial^2 T}{\partial z^2}
\label{Gr(1.82)}
\end{equation}

Created: 2024-02-27 Tue 10:31