Inquiry Dave Henry Buffalo State College

“You have two ears and one mouth – use them in that proportion.” Arnold Arons giving advice to a teacher

A B C E D A case for inquiry A B C E D

A Case for Inquiry: Constant current batteries and disappearing electricity

Constant Current Batteries A common naive conception is that a battery will provide that same electric current -regardless of what is connected to the battery. Instruction is often not effective in changing this mental model

A B C E D Current Electricity Predict – Observe – Explain (POE) Rank the bulbs in the circuits according to brightness. (adapted from White and Gunstone, 1992) A A A A AA A

Constant Current Battery Teacher: I’m curious how the electric current coming out of the battery for bulb A compares to this one with B and C and this one with D and E? Paul: Well the electric current is the same. It’s just where it has to run through. It’ll start at the negative and go to the positive obviously, but here it just runs through A and goes straight to B. Here it has to run through C then go to B then come back.” Teacher: So the current is the same? Paul: Yes. A B C E D

Constant Current Battery Teacher: How does the current coming out of the battery connected to D and E compare to the current coming out of the battery with A? Beth: It’s the same. Teacher: It’s the same? And what about B and C? Beth: The same. Teacher: If the current is the same from the batteries how can B and C be dimmer? Beth: The resistance of the bulbs as the electrons flow through. Not that the kind of bulb matters, just it takes... I don’t know what I’m trying to say here. A B C E D

A case for inquiry: Electricity is used up Another common naive conception is that electricity is something that is “used up.”

Electricity is “used up” Teacher: Ok, so if I put an ammeter say before bulb C, after bulb C and before bulb B and after bulb B. How would those ammeters compare? Maggie: This one, the one before C, will be greater than the one after C and the one after B. A B C E D

Electricity is “used up” A B C E D Teacher: How would the ammeter after A and the ammeter before A compare? Bill: The one after would be less. Teacher: And it would be the same or different than the one after the bulb B? Bill: It’d be the same as the one after bulb C, but more than the one after bulb B. Teacher: What happens to the current then. Bill: The bulb uses the energy.

Electricity is “used up” Teacher: So if you had a powerful microscope, a “magic microscope” that you could kind of see inside the bulb what would you see? Bill: Electrons go in the wire and go off, I don’t know, they like get bright so they leave the wire, I guess, like the filament so you lose them. The electrons would be going in there and then bouncing around so that they go off out of the filament. Teacher: So the electrons are creating the light? Bill: They are the light, yeah. A B C E D

Current Electricity: novel situation 1.Rank the motors in each circuit, A, B and D, according to their speed. 2.If I stop motor B, what will happen to Bulb C? (Why?) 3.If I stop motor E, what will happen to Bulb D? (Why?) A B C E D

“When the answer finally came to me, I was so excited. I would come to the end of a very difficult process only to find out that the next day, my frustrations and confusions would reappear with a new lesson. Knowing that these activities are all steps to finding out the answer to my problems will help me to keep eager and open-minded the next time I start to get frustrated.” student after many months of inquiry-based physics class

“All of the puzzle pieces had finally come together. The picture was right in front of me. I may not have expected the outcome of the experiments, but I will remember the results because I had seen and come up with the ideas on my own.” student after many months of inquiry-based physics class