A student conducted an experiment that aimed to determine the influence of different operating parameters on the potential difference across the plates of a parallel-plate capacitor. The student coupled a 10.0 μF capacitor made of two parallel circular plates, each of radius r, and separated by a distance d, to a 15 V voltage source and let it charge completely before disconnecting the source. Assume no action changes the charge on the plates. i) Determine the reading on a voltmeter connected to the charged capacitor. ii) The student increases the distance between the two plates to 5d, what does the voltmeter read? iii) Find the voltmeter's reading when the plate radius is stretched to 3r and the distance remains d.