Have you ever bought a present for a loved one where you weren’t totally sure that he or she would be enthusiastic about the present, but you figured that you could always keep it if it was a dud?
I have this hunch that a good number of “educational” gifts that parents get for kids fit in this category.
I have a further hypothesis that the gifts that the parents are really secretly hoping that they will get to keep for their very own are the gifts their kids end up liking the most.
A recent data point in support of that hypothesis: The Snap Circuits set we got for the elder Free-Ride offspring’s birthday this past summer.
After the Free-Ride offspring returned from fishing with Uncle Fishy last Sunday, we clamored around the Snap Circuits and took note of some concepts that are not obvious to kids who spend most of their time focused on macroscopic phenomenon.
Some ideas aren’t too hard to get across, like the difference between an open circuit and a closed circuit. The fact that you are snapping in the connections to make a closed loop (or snapping them out to open it) conveys that pretty concretely. And elder offspring was quickly able to deduce that the same sort of thing must be going on in the switch component (where the opening and closing essentially happens in a black box — I seem to recall the switches we used when playing with circuitry with my father were ones where you could see the connection being made or broken).
Harder to explain is just what it is that’s moving through the circuit, and how that stuff behaves, and why it behaves that way.
The sprogs understand that the stuff that you get from the batteries is electricity, and we described it as electrons flowing through (or zipping around — particle/wave duality, don’t you know) the circuit. But I suspect they’re still kind of fuzzy about just what these “electrons” are.
My better half tried to explain why the electrons would zip through the circuit in the first place, rather than just sitting tight in the batteries, by whipping out the multimeter.
Dr. Free-Ride’s better half: Behold the multimeter, device of a thousand uses!
Uncle Fishy: Well … at least three uses.
Dr. Free-Ride: And suddenly I’m in the mood for “wax lips”.
Dr. Free-Ride’s better half set the multimeter to measure potential differences and showed the sprogs the potential difference across the batteries. The strategy then was to compare the voltage difference to a potential energy difference for a book on the top bunk of the bunk-beds compared to the same book on the floor. (For some reason, the natural tendencies of physical objects on the top bunk are quite clear to the sprogs.)
Conveying the idea of resistance, for some reason, is a lot harder. In the circuit above, the light bulb lights up, by why isn’t the motor turning?
We tried to explain how the current, passing through the light bulb, came out on the other end (on its way to the motor) somewhat diminished, so that there wasn’t enough current available to make the motor go. Dr. Free-Ride’s better half used a brief game of “mercy” to try to make the idea of (physical) resistance more concrete. And, we had a happy detour through the question of what makes the light bulb light up in the first place. (Hey, look at that little curly bit of wire between the two termini! When current goes through it, that wire glows. That wire has enough resistance that the current doesn’t just zip through it, instead dissipating some of the energy as light and heat.)
When we removed the light bulb from the circuit, enough current got through that the little motor could turn. You can’t see it in this picture (since the switch was in the open position as I snapped it), but when the motor turns, the plastic propeller sitting on top of it spins for a while and then lifts off and zips toward the ceiling before crashing to earth. And then, the children shriek in delight and you have to do it sixteen more times.
But in messing around with different ways to connect the components, we discovered that putting motor in the circuit the other way around, you get a fan rather than a flying saucer. This brought the sprogs face to face with the fact that current flows in a direction. Which direction the current is flowing through the motor affects which way the motor tuns when you flip the switch. And, there’s a handedness to the plastic rotor, too — and which way it’s spinning (which is a consequence of the direction the motor is turning, naturally) determines whether it’s trying to go upward or downward!
I probably should have broken out the molecular model kits right then to explain chirality.
Anyhow, my better half took the opportunity the other morning to connect some of these new ideas about electricity with a toy the sprogs have had for ages, a little chick that makes a chirping noise when you complete the circuit between the two little metal termini discreetly located on the chick’s undercarriage.
The sprogs know how to complete this circuit themselves (the palm of one’s hand does nicely), or with a friend (each puts a finger on a terminus, then you hold hands). But for the most part, they hadn’t really thought about this as completing a circuit. (The also hadn’t really thought much about humans as good conductors of electrical current.)
Dr. Free-Ride’s better half: Are there any other ways we could complete the circuit and make the chick chirp?
Younger offspring: Wha?
Dr. Free-Ride’s better half: What if I do this?
Of course, the chick chirped.
Younger offspring: Maybe there’s electricity flowing from that part on your key that beeps and locks and unlocks the doors and that’s why the chick is chirping.
You know, it’s not the simplest explanation, but it’s an interesting one. For sure, it’s the kind of potential cause that you’d want to rule out to satisfy a clever six-year-old.