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July 07, 2013

Electronics with Xth grade

I have been taking a session (1-1/2 hrs) of electronics for the Xth grade kids. This is their only non-academic class in the week. We have so far been working on the basics without looking into any 'theory'.

First Class
We got familiar with the multi-meter as a continuity meter and went around school looking for things that will 'beep'. It was a chaotic class, the best kind to begin with and some of the girls even removed their gold ornaments to measure them.

We found that most things that we consider metallic are actually coated and need to be scraped to get to the metal and rust is not conductive.

The children also tried out measuring plants, hands, metal, wood, etc.

We put the fear of getting a shock by getting a mild shock from a 9 V battery. True, there were only two volunteers who were willing to put the leads in our mouth. It was agreed that we would not eat the circuits that we build and only work with 9 V circuits for now.

We then switched over to measuring resistance of various objects that have a high resistance, but not insulators like wood. We used water, moist skin, etc.

We also took some 1/4 W resistors and measured them as groups and got a handle of a range of resistors from a few ohms, to k ohms to M ohms. We did a few conversions between kilo and Mega and the children looked through their measurements and found that water had the highest resistance that was still measurable.
We understood how to do the above with a multimeter that required the range to be fixed manually.

Second Class
By now I had got a little more organized and bought a few prototyping boards (bread boards) and we used the knowledge of using the meter as a continuity meter and finding out how the board was hooked up. This took a little longer than expected, but it was perhaps better than explaining it each class. They also built their first circuit of LEDs in series with a resistor and the battery.

I also got notebooks for all students so I can track what they understood (no, they couldn't copy from the board yet as I didn't have a board).

They learnt that putting an LED across a battery causes it to burn out and it does look different once it has burnt out.

I didn't have enough batteries and had to dig out my stock from a long time back and got all kids of different voltages with the 9V battery. One child tried to put a switch in series with his circuit, but was unable to figure out how a two throw two pole switch works.

Third Class
By now I'm a pro and start things exactly where one of the kids gave up and gave them the nasty two pole two throw switch to put in series with two LEDs and a 1k ohm resistor.

We spend 15-20 mins figuring out how the switch works and then the groups put it together. It takes time one group manages to hook up a circuit where both LEDs light up with the switch is off and one lights up when the switch is on (they put the switch across one LED). Fantastic, now they have a circuit to debug and once they do I let everyone know what the group was able to do. What they got one LED to glow in one position and two in the other, everyone is trying to figure out how to do that now. The wheels are turning and some people come up with an alternative way of doing the same, cool.

I ask everyone to draw one of the circuits. I get feedback that they are not artists, but the LEDs looking like light bulbs starts to light up the notebooks. Some draw the exact dimensions of the bread board. I break their art class and introduce symbols for various components. There is still confusion as to how to represent the bread board, I decide to deal with this later.

Some of the folks are finished. I ask them to use the switch to light up one light at a time. They are catching on and starting to use both the poles of the switch though this is confusing their sense of direction of the LEDs. Great.

Lets work on abstractions and circuit diagrams next. Perhaps, its time to bring ohms law to the party...lets see.

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