Here lies a drinking bird

In our Thermodynamics unit students observe a drinking bird's motion to try and figure out how it works. I ask them a series of questions to guide them but several come to the wrong conclusion. Now I set up drinking birds with hot water, ice water, isopropyl alcohol and one without a cup on the second day. I ask students to apply their original explanation to the second day and that helps a few more of them. I tell students that a doctorate level thesis was written on this seemingly simple bird so it's ok if they need a one time to understand it. There are several common wrong answers:
- The liquid from the cup goes into the bird through the beak.
- Heat from the room expands the gas in the bottom bulb forcing the liquid up  (Close, can be seen if you hit the bottom with a hair dryer or hold it in your hand briefly. Try to avoid doing this in front of the kids to avoid this misconception.)
- The liquid inside the bottom bulb is heated by the room and expands.

The birds are occasionally handled too rough. I mounted one such poor bird and will add a little tombstone under it. I scraped the felt off part of the head so students could see how the top bulb was connected to the bottom one. I would like to take all the felt off of a functional head for students to compare as well. I had to add some hot glue inside the head (the cloudy white you see) in order to keep the broken fragments together. I hope to add a plaque:

Here lies a Drinking Bird

Devoted and tireless worker who only wanted

to help others understand fluid expansion and heat flow. 

Too much? 

Donate your toy to science

My kids got these killer whale bubble blowing light up toys on a trip to Sea World (thanks to grandma). The toy quality was about what you'd expect and soon they stopped working. Destined for the bottom of the outside toy box my daughter brought one to me and asked, "Mommy can you fix this?"

I said sure, then realized it was DOA. So I decided to do an autopsy. I had taken apart a bubble blower hoping to fix it and when I tested the motor directly connected to a battery I found that it was broken. I expected the same for this whale bubble blower so I started pulling it apart. Inside I found a motor, capacitor and a small circuit board that controlled the LEDs that had been in the mouth, tail and along the side. 

I was surprised to find that the motor still functioned. I tested it by using a AA battery connecting one white wire from the motor and other to the solder point on the other motor terminal. The motor spun fine and sometimes the LEDs lit up as well.

For awhile I thought that the LEDs were only lighting up when I touched the end of the capacitor across the motor terminals. Connecting the battery to the end of the capacitor, but not the solder point, the LEDs would blink. Each time I tried to recreate this though, the results were different. After some fiddling I found that just as the battery was connected or removed the LEDs would flash but not when the battery was connected for a time. Once I determined that I had a realization: I'm an idiot.

Well, not exactly. I remembered that what had attracted me to this circuit was the capacitor in it. [In my defense I was simultaneously fending off little fingers that thought the wheel on the motor looked like fun.] With the capacitor in the circuit the LEDs were only lighting up as the capacitor was being discharged.

After this project was ferried back and forth in my grading bag (I kept promising myself that this night or that prep time I would fiddle with it) a few of the wires have fallen out. I'll have to re-solder it to get the circuit to work again. If I want it to - so what do I want to get out of it?

On one hand its a practical use of a capacitor to show my students. I can either use this circuit or model more with the same premise for students to experiment with. 

Or I can scrap it for parts. I have a pile of miscellaneous electronics parts that occasionally come in handy so I can toss it in there. And I now have a motor with a fit wheel and worm gear on one end.

A great outcome was making this little motor holder. To fend off the eager "helpers" that were watching my whale autopsy I put some magnets on a mason jar to hold the motor. It worked great as an extra hand and helped hold it up high enough I didn't worry about the fan hitting anything.

I'm thinking all future dead toys will get the same treatment. Mommy needs some new parts!