LC II: A different approach

As part of the preparation we discussed that we could show the effect of different currents by putting multiple resistors in series with the LEDs. We put one, two and three resistors in series with two LEDs (bulbs, as the kids called them) and make three circuits at different locations on the breadboard.

However, as we found out there were different types of LEDs/bulbs that varied in brightness much more than what current was being pumped through them. [ You can be skip this section without loss of continuity. This stuff is keeping track of what we did so we can use it for the next course.

We had only three types of resistors a 33 ohm (1/2 watt), a 210 ohm (1/4 watt) and a 10 kohm (1/4 watt). The power supply was a 9 V battery that on loading of all three circuits would fall to around 7.8 V. The two LEDs took around 3.2 V - 3.4 V each. The currents correspondingly were around 33 mA down to 10 mA. When the current was down to 10 we could see the bulbs a little dull. Note: We had colored all the positives with a blue pen to help visually distinguish the terminal without having to look at the lengths. ]

I was hoping that the little kids would not be around and I can get down to discussing the water analogy (that hoped they would understand due to their background in plumbing). As it happened the younger children were asked if they want to attend the class.and I overheard Bharathi say ‘yes, but I would like to get a chance to do something’. This really got to me. I wondered if I wanted to teach in a particular way because I was comfortable with it or if I really felt it was what the children required. I immediately disposed off the idea of going over the theory.

We started the class by looking at the three circuits with two glowing LEDs with different resistors. I asked everyone to look at the circuits carefully and that we were going to have a game after that. With the idea of the game all the children looked at the circuits carefully.

Then I asked the younger kids sitting on one side of the table to turn around and asked the elder kids to disconnect one wire from the circuit. Senthil immediately pulled of one of the ends of the power circuit “delighting” all the bulbs. Then the younger children then got an opportunity to return the favor and pulled off a ground. Since it was quite easy to detect a hanging wire I asked one team to remove a wire and keep it with themselves. This did get quite interesting and the children realized that the grounds were as important as the power supplies. Along with this they also started registering the right colors to use for power supply and ground.

After a few rounds of this the children were getting quite comfortable with the circuits. I didn’t like the present division of the children and I paired up one of the younger children with an older one each and asked each of them to look at one of the circuits which they will need to make on their own using all the components they have.

The children I think felt that it would be easy and it was not until the circuits were pulled out in front of them and the components given to them that they realized that they were probably not completely comfortable with the idea. I was hoping that one of the LEDs would be connected flipped so they could understand that it is indeed different from a bulb and is unidirectional. I was happy that this did happen in the mistakes that were made and learnt from. Here are the lessons learnt we wrote down in class as we were building circuits: Things to be cautious of: - complete the ground for the circuit to work - direction of diode - understanding how a bread board works: The outer lines are connected vertically. The inner part is connected horizontally Interesting things we learnt and did well: - connections can be changed (R can be interchanged with LED in single circuit) - power supply can come on top or bottom as long as the circuits are the same.

As a next phase they switched circuits and tried making circuits they had not focused as much on. To aid them I drew the circuit they were making on the board and they started associating the circuit with the physical circuit.

That was it! I really enjoyed the class and I could see that the children enjoyed the class in their faces.

I realized that this is a very different way of learning circuits than I did, but comparable to the many teaching techniques we encourage teachers to use to make teaching fun and easy to learn.