Fun physics problem time. I like problems that combine different concepts, so here’s one such from Ye Olde Booke of Cavendish Problems, in a multiple-choice format. It’s not particularly hard, but I like it anyway…

A soap bubble – the film may be taken to be a conductor – of radius 10 mm and surface tension 0.02 N/m is charged by momentarily connecting it to an electrode at 6 kV. How does the radius of the bubble change?

PS. Americans, please note the correct usage of “momentarily”…