Clicky Watches

A few summers ago when by uncle and cousin came to visit us from New Jersey, my uncle would sit in our chair by our computer and shake something that make a small clinking noise. Upon closer inspection, it was his watch. He said that it didn't have a battery, and that shaking it kept it going. At the time, I didn't understand what he meant, but I remembered this this past week as we explored electromagnetic induction; his watch must have had a magnet and a solenoid in it. The shaking sound must have been a magnet, moving back and forth into and out of the solenoid. The magnet's magnetic field would have turned the solenoid into a magnet, alternating the poles to repel then attract the magnet as it moved in and out respectively. The force of the moving magnetic field on the electrons in the metal solenoid would generate an alternating current, building up charge that would eventually go to power the battery. I'm not sure how the charge was stored, as capacitors only seem to be able to discharge charge (:-) )in large, fast, quantities that would probably do to the battery something similar to what happens to galvanometers when too much current runs through them (not a good thing).

However, I guess that the generated current is not that much, as my uncle still had to sit and conscienciously shake the watch; the natural motion of his arm wasn't enough, I guess. Great idea, but I wonder if it was more trouble that it was worth. (My watch has a regular battery :-) )

Cheryl Hayashi: "Spiders, Silks, and Me"

On Tuesday February 5, I attended the lecture by Cheryl Hayashi, describing her experience from high school graduation to finding her career passion to her present day research. At first, studying spider silk seemed like an obscure profession, but after her explanation of her road to this career, I not only found it fascinating, but was also inspired to finding my own passion.
She began her presentation by telling of her path from high school to finding her career; this section perhaps had the most impact on me, as I’m currently pondering what I want to do with my life and what classes to take next year. The fact that she found her life’s passion from a requisite class and a small part time job really says that anything is possible. It also encourages you to take every opportunity presented to you, for you never know what may turn out to be your life.
Aside from the inspiration, I also learned a lot about spider silk that I never knew before. I had known that silk was comparatively much stronger than many things we consider very strong, but I didn’t know just how strong that was until I saw the comparison. I was also surprised to learn of the many different types of silk that one spider can produce. And a hundred and fifty yards of silk from one spider! Wow. I hadn’t known there was so much to just spider silk alone; and as she said, one answer brings up ten more questions, like: I wonder what else there is to study that contains more than meets the eye? Perhaps one of those could be my passion. I’ll just have to wait and see.

Homework By Lamplight...

As I was sitting doing my Physics homework wondering what I should do my blog on, I began doing a sample problem about current, power, and resistivity. All of a sudden, it his me- I have a very close-at-hand example of all three of these: the lamp next to my computer. It has a bulb that contains two filaments, and the lamp is made in such a way that it can produce three different levels of light: one filament, the other filament, and both together. As I worked on problems pertaining to legnth of the resistor, cross-sectional area, resistance, power, and current, I began to wonder how the bulb worked from a Physics standpoint. This is what I have decided: there are two possibilities for this bulb. The first possibility (depicted above) is that each of the filaments have different legnths, but same cross-sectional areas. Since R=(coeff.)L/A, the filament with the longer legnth would have a greater resistance than the shorter one. Then since P=(I^2)R, and I(current) is the same for each of the filaments since the current comes from the same source, the power in the longer/higher resistance wire would be greater, resulting in more electron movement and more transfered energy to the filament's atoms, and therefore more light.

The second possibility was that the filaments have different cross-sectional areas but the same legnth. Then, since R=(coeff.)L/A, the filament with the smaller cross-sectional area would have the greater resistance. Then since P=(I^2)R, and I is the same for both, the power for the thinner filament would be larger, resulting in more collisions and more light.

There is actually a third possibility: the filaments could have both different areas and legnths. However, companies may want to save money by using the same wire, as well as try to increase the longevity of their bulbs by using the same thicker wire with different legnths. Or would they want to use the thinner one so that the thinner filament will break more quickly so consumers will have to buy more? :-)