Tuesday, March 20, 2007
Don't teach that right hand rule
The former includes the right hand rule for determing the direction of the magnetic field around a current-carrying wire. This is a tough row to hoe, as it requires students to have a modicum of agility in thinking in three dimensions. My experience tells me that high school students have few opportunities to navigate the geometrical challenges of three-dimensional space. But the state of California wants its physics students to know this, so I teach it. I introduce it with a lab activity.
Among the things to leave to future physics coursework, I would include the current-field-force right hand rule. You know, the one involving the mutual perpendicularity of current, magnetic field, and magnetic force. Students are reeling from the 3-D demands of the first right hand rule. So why add this insult to their injury? What's the payoff? What gift does this knowledge bear that makes the pain of learning it worthwhile? In high school? Even the great state of California deems it non-essential.
Basic electromagnetism is rife with intangible fields and geomagnetic mayhem. There's some counter-intuitive stuff in this material. Can't we save this bit of trivia for another, later course?
Oh, and don't get me started on the left hand rule. (You really should click that link if you want a laugh.)