https://blogs.imperial.ac.uk/videoarc...
Professor Eric Laithwaite (1921-1997) of Imperial College London shows how a consideration of shape and size has had a profound effect on the design of electro-magnetic machines.

This is one of a series of 16mm colour films made for schools. They were all made in Eric Laithwaite's "Heavy Electrical Laboratory" in the Electrical Engineering Department at Imperial College London.