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? :-)

Blue Sparks

Perhaps some of you who read my post a few weeks ago saw my mention of a large spark my dad created on our trip to Alaska. Well, here's more details.

If you have ever been somewhere dry, you know that static electricity is something to be feared. But on this trip to Alaska, we were staying in a hotel that required walking about twenty meters from our door to the elevator, all the way on carpet. One morning, my dad, being still a young boy at heart, decided to drag his feet along the carpet to see how much static/electrons he could accumulate. By dragging his feet, he accumulated extra electrons, giving himself a net negative charge, increasing with the amount of dragging. Having discovered that the panel on the side of the elevator was grounded, he slowly moved his hand towards the panel. However, he had accumulated so many electrons and potential energy that all of the excess electrons quickly left him for the grounded object, even before he touched it. The large discharge of potential energy, energy converted to kinetic energy for the quickly moving electrons, caused a visible spark coming from my dad's finger, quickly followed by an exclamation of "OUCH!" along with a slight jump. The electrons then probably were transfered to the ground, where they quickly spread out equalizing the charge, effectively canceling it out. Perhaps more electrons moved within the building back to the momentarily positively charged floor, so some electrons going to the ground ended up back in the building. But, like I said, the spark was a bluish color, and very bright. After that, my dad and I discovered that walking while rubbing our hands on the wooden handrail, as well as touching the elevator panel through our jackets, lessened the severity of the shock. I'm glad I don't have to do that on a regular basis. If we ever go back, I wonder if my dad will have learned his lesson, or if the young boy inside of him will prevail again? :-)

P.S. My mom was folding laundry once again (thank you, Mom!), when a sock which was held onto a shirt by static electricity from transfered electrons from the dryer came flying off when she shook it and landed right back in the pile without her noticing it. It was hilarious. :-)

Ions for your hair

Many years ago, my grandpa gave me a hairbrush for Christmas. However, this was not your ordinary hairbrush; this particular one claimed that it used ions to help your hair. It was called the "Ionic Hair Wand Pro," and if I recall correctly, it was supposed to make your hair more managable by causing it to tangle less. (At the time, I was about nine years old and didn't like to brush my hair...at all) Although I'm not sure it helped any, I was contemplating electric forces and charges when I remembered this brush. However, I had never known how it worked, but with my new-found Physics knowledge, I've formed a theory about how it works.

One of the parts of hair that makes it tangle is the outer part, which is make up of little plate-like flakes that can stick out and catch on other hairs' flakes, causing hair to become more tangled. So, my theory is this: the hairbrush sends out ions from a small vent in the middle of the hairbrush that come in close proximity to these flakes as the brush travels through the hair. When these charged particles approach the neutral flakes, they will cause them to become charged either by attracting electrons if the ions are positive, or by repelling electrons if the ion is negative (I'm not sure what the brush sends out). When it does this, the flakes will gain a charge, but they will also create an equal and opposite charge in the middle of the hair either by pulling electrons away from it, creating a positive middle, or by pushing electrons into it, creating a negative charge. Thus, the flakes and middle part of the hair will attract, because opposite charges attract with an equal and opposite force. This will then cause the flakes to lay down flat on the hair, keeping them from sticking up and keeping them from catching on to other hairs, causing the hair to be less tangly. Unfortunately, it didn't seem to work for me; however, that may have been more the fault of my lack of frequent conditioner use and my tendency to always wear my hair down (even in the wind). I wonder if it still works? I should try it out... :-)

Snap, Crackle, Pop!

No I'm not eating rice krispies, although rice krispie treats do sound good right now (although too sugary). Actually, as I was sitting trying to do my homework and watch TV at the same time, my mom was being very nice; she was folding my clean laundry, strait out of the dryer. Although I am very grateful as I know how long that takes, I don't usually pay attention unless I'm helping or I need to monitor the dryer so that my already-too-small-in-the-arms tops don't stay in too long. But as I was drawing polar coordinate graphs, I heard something very familiar: "rackle crackle crackle." I knew immediately what it was: it was my mom unsticking clothes from each other, held together by static electricity. But today, this sound was different, for I had read the assignment on electric charge, and I knew exactly what was going on. When the clothes had been tumbling around in the dryer, the electrons in the outer parts of these items would rub off, being transfered to the objects on which they were rubbing, such as the walls of the dryer, or other clothes. In this case, these two objects built up enough opposite charge to attract each other, since opposites attract. The forces that each exerts on the other are equal and opposite, as well as strong enough to hold them together. When my mom tried to pull them apart, the electrostatic forces fought back, keeping the items clinging together, even to the last clinging fibers which still point directly towards the other object. However, I believe the crackling sound has something to do with returning the charge to equilibrium, but I would have to read more. Oh also, just as a warning: if any of you ever go to some place dry,(my experience is from Alaska) don't drag your feet along the carpet, and don't go touching metal objects that may be touching the ground, because you almost certainly WILL get shocked. You should have seen the spark my dad created(it was blue).

The Thermodynamics of Baking

I love baking. However, I love eating the food even more than the work that goes into its preparation, so combined with my laziness and need to stop eating junk food after the extremely tasty month of December, I don't bake very often. However, last night my dad did that for me; he made a batch of very yummy biscuits (one of which is pictured here) that even though I had just eaten a large dinner and half a cinnabon I immediately dove into. (I need to learn some self control :-) ) But this morning while considering whether to eat another one, as well as pondering thermodynamics in daily life, I thought, "Hey! Biscuts are full of thermodynamics, at least the baking process anyway." When the oven is turned on, the coils producing the heat begin to heat up the air inside the oven by conduction, which then circulates by convection due to the differing densities between the warm and cool air, eventually bringing the entire oven up to temperature. The heat is prevented from escaping by the walls of the oven which, I would guess, are covered with a high specific heat material and/or a material that is designed to reflect the infrared waves from the hot air and heating coils. Then when the biscuits are put in, they begin to heat up by conduction as well. However, the outside will heat up faster, as it has more contact with a larger heat source than the inside does. Then when the outside begins to cook and get hard, it doesn't allow for the expansion of the biscuit anymore as the temperature goes up, turning an isobaric process into an isochoric process. However, that means that as the temperature of the inside rises, the pressure builds. But the outer layer isn't strong enough to contain the pressure, so it splits and releases the pressure, allowing the inner contents to expand once more, just like this biscuit started to do, but the picture's not good enough to see it very well. But sorry, there can be no more pictures of that biscuit to show the split; notice that the biscuit is sitting on a cutting board. It was eaten with strawberry preserves soon after that picture was taken. Yum!