端子電圧を $V$[V],誘導起電力を $E$[V],電機子抵抗を $r_{a}$[$\Omega$],電機子電流を $I_{a}$[A],界磁抵抗を $r_{f}$[$\Omega$],界磁電流を $I_{f}$[A],界磁巻線電圧を $V_{f}$[V],負荷電流を $I$[A] とする.
\[\begin{eqnarray}V&=&E-r_{a}I_{a}\\I_{f}&=&\frac{V_{f}}{r_{f}}\\I_{a}&=&I \end{eqnarray}\]
\[\begin{eqnarray}E&=&V-r_{a}I_{a}\\I_{f}&=&\frac{V_{f}}{r_{f}}\\I_{a}&=&I \end{eqnarray}\]
Mathematics is the language with which God has written the universe.