Toepler's law (1906) states that the resistance of an electric arc at any time is inversely proportional to the charge which has flowed through the arc:
where I(t) is the current in the arc discharge at time t, and D is the gap between the electrodes. The parameter is a constant whose value is .
- Toepler's law (PDF)
- Toepler, Annalen der Physik, 1906; 4: 191. (original publication)