In physics there is this thing in learning electromagnetism called the 'right hand rule'. It works like this: You point your right thumb in the direction of the electric current, your fingers in the direction of the magnetic field and then your palm will point in the direction of the magnetic force on the current. So, given any two you can orient your right hand to find the direction of the third vector. So, I had a number of transparencies (this is WAY before LCD projectors) for practice and it was always quite fun to see the kids go through their contortions to orient there right hands correctly.
On this day though, it was my 4th time through it and it was scalding hot in my room. The lights are low to use the overhead and we're going through the various situations. I can watch the kids pretty well to see if they are orienting there hands correctly. We'd done several and then I spot this girl near the back using her LEFT hand. For crying out loud. . .
LISA! This is the RIGHT HAND RULE. You have to use your RIGHT THUMB for the current!
Lisa looks at me and holds up her right hand and sweetly says, "Mr. Welty, remember? No right thumb."
Wanna get away? Yeah, Lisa doesn't have a right thumb. I knew that but in the heat of the teaching moment I forgot. Oh yeah I wanted to get away. . . big time!
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I had a similar moment as a kid. We were gathered around our grandmother. Someone had said that some people fold their hands with right hand dominant, others with left hand dominant. I asked my grandmother to show us which way she folded hers. Duh, grandma only has one arm (lost it as a child in a meat cutting accident)!
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