A spherical metal collector in an industrial electrostatic dust precipitator becomes negatively charged.
State how the strength of the electric field surrounding the collector changes as the radial distance from the surface of the collector increases.
During a maintenance procedure, a grounded discharge probe is moved towards the charged collector until a spark occurs between them. The spark transfers 0.85 J of energy, and a charge of 2.5 μC2.5\ \mu\text{C}2.5 μC is transferred. Calculate the potential difference between the collector and the probe.