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February 25, 2007

Learning Circuits (LC) I: Let there be (some) light

Krishna had collected a bunch of different types of LEDs over time with the hope of being able to make torches out of bamboo. He had also hoped to use the LEDs to make lights for the 24 V DC supply that comes from the solar panels and battery.

The effort to grow while keeping in mind the environment and the consumption to a certain extent is quite a remarkable aspect of Tulir. Tulir’s activities of the school and technology course as well as Anu and Krishna’s home work off solar power.

The villages do receive electricity. However, the supply is erratic (just as the telephone lines that were down a good part of our visit there). Apparently, during the summer afternoons when it’s hot and people want to be indoors the power would tend to be out. The people who live near their farms and not in the villages itself do not receive any electricity. General lighting on the roads is pretty minimal and only on the main street that is lined with homes. The poorly lit street that is presently being constructed is perhaps a reason why most of the children go home near sundown.

As I started the class the younger children who are also at Tulir in the morning also joined us. The class started with me bringing up the puzzle I had given for them to solve the previous morning. I was surprised that they had not even attempted it. I tried giving hints, but realized that the boys were too scared to try to understand it. By this time the younger children had start to get it and I was worried that I was probably hurting their confidence even more by doing this. At this time someone had a good idea of doing it physically. We made some hats with newspapers and made the people stand one behind the other and calculate the color of their hats by the hint given by the last person in the line. After a few attempts and explanations the children started to get a slightly watered down version of the puzzle and it seemed to make them happy.

The rest of the curcuit class is not much to talk about. I had read in a few scraps of paper that Krishna had collected that the voltage of the LEDs are in the ballpark of 3.6V. Beyond that I had made no preparations. I built a simple cuicuit with the LED and a resistor and the positive was that the resistor lit up. I decided that the best thing to do will be to measure the voltages and then learn about why different voltages are such. As we measured the voltages we realized that the battery voltage had dropped from 8.5 V to around 8 V. I tried explaining the resistance of the battery and realized that they hadn’t heard of ohm’s law. Then I tried to explain the resistors as fat and thin pipes, but I had not thought through all these and the kids understood the explanation but not how it was connected to the circuit at hand. This was especially because in their jargon current, voltage, power and resistor all meant the same thing. At this point I decided to give up think through my analogy and explain it the next class.

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