My students asked me this question the other day, and while slapping together an animation of electromagnetic induction I gave it some thought.
This program itself is really simple. It took about 15 minutes.
But that’s not counting the half hour I spent searching the web for an image I could use to illustrate magnetic induction and not finding one I could use.
Nor does it count the four hours I spent after I got the animation working to get the program to take screen captures automatically. Of course, I must admit that figuring out the screen captures would have gone a lot quicker if I’d not had to rebuild all my permissions on my hard drive (I’d recently reformatted it), and reinstall ImageMagick and gifsicle to take the screen captures and make animations.