The rising part of the current waveform observed when discharging an electrostatically charged person or test generator shows some phenomena which have not been explained satisfactorily. This paper describes an attempt to understand these effects using both experimental and numerical simulation. A special rotating system to simulate a defined, variable closing speed of contact has been built. The length of the arc is also measured and it can be shown that a strong correlation between arc-length and rising slope at a given voltage exists. This result is compared with a theoretical model using the law of Toepler