Final answer:
The physicist who developed the first spark-gap tube generator in the 1920s, leading to the electrosurgical generator, was William Bovie.
Step-by-step explanation:
In the 1920s, the physicist who developed the first spark-gap tube generator, which led to the creation of the electrosurgical generator, was William Bovie. This is not to be confused with Wilhelm Röntgen, who is well-known for the discovery of X-rays in 1895 by experimenting with cathode ray tubes. While Röntgen's discovery was pivotal and won him the first Nobel Prize in Physics in 1901, it was William Bovie who later contributed to the development of electrosurgical devices.