A static electricity generator has a metal dome that becomes positively charged. State how the strength of the electric field around the dome changes as the distance from the dome increases. An earthed metal conductor is moved towards the positively charged dome until a spark jumps between them. The spark transfers 0.48 J0.48\text{ J}0.48 J of energy, and 1.5 μC1.5\ \mu\text{C}1.5 μC of charge is transferred. Calculate the potential difference between the metal dome and the earthed conductor.