All Charged Up

I come from a time when girls were not encouraged to take science classes.  I struggled with math in high school, so when my teachers said I didn’t need to take chemistry or physics–the implication being I’d struggle there, too, and besides, why did a girl need chemistry or physics?–I just smiled and considered myself lucky. Big mistake. I should have been more assertive–I should have known I would be missing out. 

My good friend and colleague Cheryl McLean invited me into her class last week to observe a demonstration lesson in AP Physics I. As I watched, my own high school experience came rushing back. I realized what I had missed a long time ago, and I’m grateful now, after all these years, for the invitation to learn, right along with this class of–get this!–twenty-one girls (and one boy).  

Here’s an account of that class:

While students settled into their seats and readied their laptops, notebooks, and pencils, Mrs. McLean briskly conducted the business of the day:  due dates announced for future assignments, current papers collected, attendance taken. Then she directed the students to gather in front of the demonstration counter for an introduction to the fundamentals of electric charge.

McLean pie pans 2For the first demonstration, she used an electroscope and a charging rod. She brought a negatively charged rod close to the electroscope and the two metal “leaves” inside pushed as far away from each other as they could; a positively charged rod brought them together.  The principles: attraction and repulsion.

Ben Franklin, she told the students, coined the terms positive and negative charge.  In that way, she tapped into our collective memory of his legendary experiment with lightning.  Franklin, even I knew, wanted to establish that lightning carries electricity.  Indeed he proved that.  The negative charge from a lightning bolt struck his kite and traveled down a wet silk thread to a key at the end of the thread.  When Franklin touched the key, he received a shock.  Classic electrodynamics.

For the next demonstrations, Mrs. McLean used the van de Graaf generator, a piece of scientific equipment that looks like a giant silver lollipop.  The van de Graaf generator produces a charge by dragging a rotating belt over copper cones.  The surface of the metal “lollipop” becomes charged.

McLean peltMrs. McLean brushed the surface of a rabbit pelt with a comb. When she perched the pelt  on top of the device, the individual hairs stood on end.

Then came the “pie pan demo.” One-by-one, chicken pot pie pans, a minute ago nested in a stack on top of the van de Graaf generator, launched into the air, seemingly on their own.  Students had already observed the generator’s ability to charge an object.  Now they saw that a collection of charge can produce an electric force that exceeds the gravitational force acting on a single pie pan.  Thus, the charged pie pans achieved lift off and sailed into the air.

Finally, Mrs. McLean showed the students how a charge “travels.” A student touched the van de Graaf generator, received the charge, and then touched a small pool of water on the counter.  The resulting electric shock traveled, wrist to wrist, along a line of students who were holding hands. The last student was touching the counter, too—and the charge grounded.

McLean tarveling shock

AP Physics has the reputation of being a difficult class:  Tough topics, high level math.  To explain the phenomena that the students study, Mrs. McLean starts this unit, and others like it, with a demonstration of the principles the students will later explain mathematically.  “It’s not enough to do the math that explains the phenomena.  It’s important for students to know through experience what actually happens,” says Mrs. McLean.

Later in the class period, when the students were working the equations that explained the phenomena, I did get lost.  It had just been too long.

A week later, I went back to AP Physics I to ask the students if and how the demonstrations had helped them when they started doing the math.

“They helped me visualize the movement of the electrons and the protons to make positive and negative charges,” said one student.

“It was more interesting with the demonstrations,” added another. “We paid more attention.”

The final word came from a third: “And it was more fun!

Indeed it was.

I have also observed high school chemistry classes in my capacity as an instructional coach.  (You don’t need to know the content to recognize good teaching or to help someone adjust their instruction to be more effective.)  I know now that I could have understood chemistry.  I could have understood physics.  After all, I did take the full four years of math, which ended then with trigonometry and solid geometry.  The recommendation that I not take those science courses in high school is really a reflection of the time period in which I grew up.  No malice was intended.  My teachers were simply short-sighted–and I didn’t believe in myself enough to question their recommendation.

I could mourn my loss. I could get angry at having been cheated out of an education in science.  But really, I’m more grateful than I am sad or mad. Grateful to my colleagues who have invited me into their classrooms to help them, but who, probably unknowingly, have helped me as much.  In the past several years of coaching, I’ve learned quite a lot–in science, in math, and in every other subject, too. In a way, I’m getting to repeat high school. And it’s a privilege, not a penalty.  In fact, I’m all charged up about it.  Still.  After all these years.



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