AC/DC Circuits!

As our last unit, we learned about electricity, specifically DC circuits. DC circuits are electrical circuits that keep electrons in a direct and constant flow if the circuit is closed. Batteries are used to power these circuits. The current of the circuits is like the flow rate in plumbing pipes, the voltage is like the water pressure, and the resistance in each bulb is like the size of the pipe (friction, essentially).

This is a diagram of a DC circuit in series. In this circuit, the energy created by the batteries allow the electrons to flow through the circuit. The bulbs are dimmer than normal because the voltage is split between the two bulbs from the batteries. The current remains the same throughout because there is nowhere for it to split.The circuit is just one loop so the current stays constant even when the voltage changes due to the resistors. This is a series circuit because the electrons have only one "series" of wire to travel through. If one of them were to be removed, neither bulb would work because the bulb serves as a connection. The resistance of each bulb is like a friction that slows down the current and since it is in one series of wire, the current is slowed through the whole thing.

This is a diagram of a parallel DC circuit. This circuit is different because there are two paths for the electrons to flow. Unlike the first one, if one bulb is removed, the other one will not be affected because electrons still have a way to flow through the other one. The current isn't affected by the resistance of each individual bulb because the electrons come back together after they go through each individual bulb. This is why the bulbs are brighter. The voltage is like what water pressure would be in some plumbing pipes. Since there is a fork in the path, the water pressure remains the same, and then after it goes through the "friction" of the resistors, it just comes back together. The resistance of the bulbs does not play a huge role here because since there are two paths, the current doesn't affect each bulb.

Finally, we have a complex circuit, with a bulb in a series with two bulbs that are in parallel. As you can see, the two bulbs in parallel aren't as bright as they were before. This is because the bulb in circuit creates a voltage drop like in the first diagram, therefore making the bulbs in parallel dimmer. If one of the bulbs in parallel is removed, everything still works the same. However, if the bulb in series is removed, everything stops even when the other two are in parallel. This is because if the bulb in series were removed, the circuit would be incomplete. In this circuit, the bulb in series acts the same as the first diagram for the two parallel bulbs. The "friction" in the resistor of the bulb in series slows the current down so that when it gets to the parallel circuit, the current still splits like normal, but the current is slower to begin with.

The voltage and current are different in each of these because they all have different means of transporting the energy. When they're put together, it's a mixture of both ways to solve.

2011 Sports Illustrated Log Ride: Wavy Physic's!

After hours and hours of hard labor, slaving over band-saw's and drills, we have completed our 2011 Sports Illustrated Log Ride. The boat runs through the ride smoothly, packed with tons of fun turns. I speak for us all when I say that I gained so much knowledge about physics in the real world during this project. Getting to see everything run so smoothly and just the way we wanted, and then the math involved to make it all do so, made it very easy to see the relations between the technicalities of it all and real life. Here is our presentation of the project on a Prezi, and you can take a closer look on our team site!

https://sites.google.com/a/parishepiscopal.org/physics-honors/amusement-park/team-4

Sports Illustrated Log Ride on Prezi

AAPT Photo Contest: Refraction of Regular Light

For my photo for the AAPT photo contest, I took a prism and an LED flashlight in a dark room, and used them both to create a beautiful, for the lack of a better term, array of light. Since I used an LED flashlight, the prism couldn't show the different colors of waves that make up the one light (i.e. the color spectrum of a rainbow). Had the sun been out and bright enough on the day I was doing all of this, I would've been able to use the sun's light and get a broad spectrum of colors.



The different angles of the glass prism make the light reflect in different ways. The light enters the prism, going from one medium to another (air to glass) which then causes it to slow down or speed up (in the case, slow down) and refract in a different direction. The incident angle (the angle in which the light source was directed at the prism) was the reason as to why the light was refracted the way it was. If I had placed the light source lower, higher, more to the right, or more to the left, I would have gotten different outcomes. Here are pictures of the prism I used, and the outcome when I shined the LED flashlight through it.

The third photo (of the refracted light) may seem a little blurry but if you look carefully, it is not. The distortion of the light and everything just isn't perfectly clear because the light source wasn't perfectly aligned, therefore the glass on one side of the prism and the glass on the other create slightly different angled light.

Catchin' Some Narly Waves Dude!

The electromagnetic spectrum is the scientific term for the different types of radiation. Radiation is simply energy that travels through anything, including a vacuum in which air is not present. This is one of the things that makes them so unique. As the waves travel, they spread out as they go. Hotter sources create higher amounts of radiation while cooler create lesser, such as an x-ray which creates a very large amount of radiation while radio waves create just enough to communicate. The seven types of electromagnetic waves are (in order from least to highest amount of radiation): radio, microwaves, infrared, visible, ultraviolet, x-rays, and gamma-rays. Radio waves have a very long wavelength with a low frequency. Microwaves have a smaller wavelength but still quite long in comparison to other waves. Infrared waves have a noticeably shorter wavelength.Visible waves, which include things like lamps, light bulbs, etc., have a wavelength similar to infrared waves, as do ultraviolet waves. Ultraviolet is a type of wave that is primarily created by the sun, i.e. the rays of sun the beam down on the earth. Finally, the two shortest wavelengths are x-rays and gamma-rays. X-rays have to have a short wavelength to see into our bodies, while gamma-rays, the highest form of radiation is what is found in radioactive substances.

Two types of waves that some people find most interesting are gamma-rays and x-rays. Gamma-rays have a wavelength starting around .03 nanometers and frequency starting around 6.009 x10^10 GHz. These get progressively smaller and bigger, respectively (the size and frequency of the waves). Instances where gamma-rays occur include medical therapy, nuclear reactions, and things in space like supernovas and stars. Gamma-rays have the most energy of any of the waves. It is said that gamma-rays can emit more energy in 10 minutes than our sun can in its entire 10-billion year expected lifespan. Humans cannot see gamma-rays, it takes a special type of telescope to see them.

Second, x-ray waves start at about 3 nm and a frequency of 2.459 x10^7 GHz. They get smaller and bigger, respectively (the size and frequency of the waves), until they reach .00623 nm and 4.809 x10^10 GHz. X-rays are used primarily for medical diagnostics to view bones and other parts of the body. There are classic x-ray machines, but now there are things like CAT Scans and MRI machines which view your body more in depth. Our sun generates mostly x-rays, even though it is visible light, the waves themselves have characteristics of x-rays. High energy particles emitted from planets in our solar system can be seen through certain telescopes because they are hot enough to emit x-rays. The sun's x-rays aren't harmful to us because our atmosphere absorbs most of them. However, the use that most everyone knows about in the world is medical diagnosis because of the energy the x-rays emit that isn't powerful enough to harm us, but it is powerful enough to take images of things under our flesh.

This is the burst of a gamma-ray when a black hole is being created, pictured 12.8 billion light years away from Earth. Obviously if we can see it that far away, the energy must be pretty high. This picture was taken with NASA's Swift satellite in deep space. This object is among the most distant objects ever detected.

This is an x-ray of somebody's neck/spine. The energy transmitted from the x-ray is powerful enough to see inside the body.

http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html

http://missionscience.nasa.gov/ems/01_intro.html

http://lectureonline.cl.msu.edu/~mmp/applist/Spectrum/s.htm

http://www.universetoday.com/wp-content/uploads/2008/03/grb.jpg

http://www.kitsapchiro.com/yahoo_site_admin/assets/images/x-ray.131180558.jpg

Energy: What Makes Life...Life.

For our reflections on our unit over energy, we were required to think of a real life situation that was related to what we were studying. For my topic, I chose football. Instead of just recollecting what we learned and what we didn't, this required us to critically think about the lesson in real life, not just scenarios made in the class room.



Attributions for my images:
http://www.statefansnation.com/wp-content/uploads/2009/06/football.jpg
http://cdn2.sbnation.com/imported_assets/406750/football_spinning.gif
http://www.webweaver.nu/clipart/sports-football.shtml
http://www.scasd.org/25452078145137270/lib/25452078145137270/football_ref_touchdown_hclear.gif

Mythbusters: Physics In Action

For our latest experiment, we duplicated what would be an episode from the famous Discovery Channel show, Mythbusters, in our own way. We were given two "myths" that had to do with physics in action and we had to do what we could to prove or disprove them. 

MYTH #1:

An object always moves in the direction of the net force exerted on it.

At first glance, this may seem obvious: yes. However, it's possible for this to be proven wrong if looked at very closely. We predicted that if and object doesn't always move in the direction of the net force exerted on it. If this were true and you were to push an object on wheels in a certain direction, then as soon as you stopped pushing, the friction being the only net force after the applied force is taken away would cause the object to go in the completely opposite direction instantaneously. To conduct our experiment, we used what we  called a "mancoaster". We put one of us on said coaster and another team member pushed the coaster. Here is our free body diagram of the situation after the applied force is no longer present. 

ΣF = Ff because ΣFy = Fn - Fg and when they both equal each other they cancel out, therefore the net force is just the force of friction. With this being true, we busted the myth by proving that even though the net force on the coaster is in one direction the mancoaster continues to move until it comes to a stop, but never does it actually move in the direction of the net force.

MYTH #2:

An object always changes its motion if there is a force exerted on it by other objects.

If an object were to always change its motion due to any force exerted on it by other objects and we were to roll a bowling ball and hit it with a small highlighter, then the bowling ball's motion would change. However, we predicted that this myth is NOT true, and that if we were to perform this experiment that the bowling ball's motion would not change. Our experiment was simple: we took a bowling ball so kindly supplied to us by Mrs. Gende and found a hall in which we could roll it. We proceeded to roll it and closely examined it to see what would happen to it if we were to throw a highlighter at the rolling ball. Here is a free body diagram at the exact moment that the highlighter hit the bowling ball.

Our experiment busts the myth for the reason that despite the fact the highlighter hit the ball while it was rolling (quite hard, might I add) the ball did not stop rolling or change direction. It would take a three dimensional FBD to truly show the highlighter hitting the ball, but nonetheless, the ball was not affected.

Conclusion

The two myths at first seemed like they'd be easy to prove as true, but by actually sitting down and reading them carefully and fully thinking of every possibility, we realized we could easily disprove them. Some could debate on the busting of the second myth because they could say that the ball "slowed down a little bit" or that it "ever so slightly changed its course". Regardless, this doesn't make these myths true. It just means the way we decided to disprove it isn't "100% correct" according to some.

People believe these myths in the first place because they do not look deeper into the possibilities. One could be a leaf hitting a bird in flight. Unless the bird freaks out, it will most likely keep flying in the same direction. This is beside the point though, it just shows how some people just wouldn't see the deeper possibilities. As for the first myth, people believe in this often because if one was to simply look at an object in motion, they only see the net force that was used to put it into motion, not the forces acting on it in the air or one the ground, such as air resistance or friction.

Once again, bye for now Physics World.