The chocolate crumb mystery this story begins with Problem. As part of the investigation of the biscuit factory explosion, the electric potentials of the workers were measured as they emptied sacks of chocolate crumb powder into the loading bin, stirring up a cloud of the powder around them. Each worker had an electric potential of about 7.0kV relative to the ground, which was taken as zero potential.

(a) Assuming that each worker was effectively a capacitor with a typical capacitance of 200pF, find the energy stored in that effective capacitor. If a single spark between the worker and any conducting object connected to the ground neutralized the worker, that energy would be transferred to the spark. According to measurements, a spark that could ignite a cloud of chocolate crumb powder, and thus set off an explosion, had to have energy of at least 150mJ.

(b) Could a spark from a worker have set off an explosion in the cloud of powder in the loading bin?