## Wednesday, July 28, 2010

### Wednesday - July 28

This was the most challenging day yet for the students. They had lots of hands-on work to accomplish. They completed making performance measurements on the prototype linear electric generator and are now getting ready to prepare a presentation of their scaled up designs.

We did some complicated mental gymnastics this afternoon involving estimating numerical answers to difficult questions without resorting to a calculator. They caught on very quickly. For example, they measured the electrical resistance of the generator coil, which was approximately 38.5 ohms. I told them the electrical resistance of the wire used was .108 ohms per foot. I then asked them to calculate, without using a calculator, what the appriximately length of the wire was on the generator using the tricks we showed them. They rounded .108 to .11 ohm. If it was .1 ohm the answer would be 385 feet. If we subtracted for the extra .01 ohm we would subtract 38.5 feet. Round this to 40 feet. Subtract 40 from 385 and you get 345 feet as the approximate length of wire. The correct answer is 356 ft. Their estimate was correct to within within 3% and they did all of the arithmetic in their heads.

When Rich Burgess was discussiing engineering ethics in the last hour today, he asked the students who would benefit from what they had learned in the last two weeks. One young lady said, "Us." When Rich asked her what she meant by "Us" she quickly replied, " Us, the engineers." Clearly she now thinks of herself as an engineer. That made my day!

I am very proud and impressed by these students. They have a bright future ahead of them regardless of the field they enter.