Currently in Currents...

One thing that impacts all of our lives is electricity. It's how we as humans basically survive, from cooking our meals to managing enough light for ourselves. Electricity has even shaped how we get our entertainment! In getting our electricity, as I mentioned in the other electricity post, there are two types of currents; direct current (DC) and alternating current (AC). In the below movie that I've created (please tell me if it doesn't work! I've just tried a new software, and I don't know how it turned out...), there is a brief explanation of what each current is, which everyday appliances they run through, and a slide presentation of how each current runs.

Now that the video is finished, DC and AC are prevalent in our everyday lives. DC powers anything we have that runs off of a battery, like our cell phones and laptops. AC, on the other hand, powers things that we plug into the wall, such as lamps and dishwashers. It's important to know which items run on which current, because the wrong current could ruin an appliance.

There are also DC-AC converters. This is because DC is normally low voltage, and AC is high voltage. These converters take the low DC voltage and raise it before turning it into AC. DC is turned into AC because AC is can better manage the increases in voltage.

Upon researching AC, I found that most countries use an energy system devised on either 50 or 60 Hz; in Japan's case a mixture of the two. When I saw this, I decided to make my application on why all of our electricity isn't based on AC.

DC is electricity found when there is a definite positive and negative terminal. It also doesn't have a very high voltage. AC, on the other hand, can be used to build extremely efficient power generators.

So what are the advantages of using DC? The first major one is that due to the low voltage DC deals with compared to AC, it is less dangerous. DC is also cost efficient, as it doesn't require an inverter. This system is also energy efficient as well, provided there are no long wires. The system itself is relatively simple. However, the best use for DC is in smaller homes, and a converter will be needed in order to use most appliances.

Using AC, on the other hand, is great for large places. A converter wouldn't be needed, and long wires ensure that the system is being efficient. The equipment needed for safe distribution is widely distributed, unlike DC equipment, which is harder to find. However, to hook AC up to a home power system is extremely expensive, and requires an inverter.

I suppose that when looking at all of this information, using both types of current does help depending on how big the place is and how much electricity is needed. It would be kind of silly to have a cell phone on AC, where somone could easily electrocute themselves, or a dishwasher on DC, using twice as much energy as it would normally take.

Further digging showed me that DC power systems are, in fact, returning to common use. This YouTube video, made by phsavage, explains why that is.

Sources:

"Ac or Dc." Solar Alaska. N.p., n.d. Web. 26 Apr. 2012. <http://www.solaralaska.com/primer/ac_dc.htm>.

"What Is Alternating Current (AC)?" All About Circuits. Design Science License, n.d. Web. 26 Apr. 2012. <http://www.allaboutcircuits.com/vol_2/chpt_1/1.html>.

Wikimedia. "Alternating Current." Wikipedia. Wikimedia Inc., 18 Apr. 2012. Web. 26 Apr. 2012. <http://en.wikipedia.org/wiki/Alternating_current>.

Back in... Light?

Back in Black is one of the most well-renowned songs from the band AC/DC. However, in physics AC/DC means something totally different; alternating current and direct current. The band even alludes to this meaning in one of their more famous logos (something I've always found hilarious).

Before I start talking currents, let me first explain about electricity. Electricity is defined as any phenomenon associated with motionless or in-motion ions. For a current to be able to move, there must be a circuit. This circuit allows for the ions to move from a positive end to an element in the circuit, providing it with power before returning to the negative end. Batteries, wires, and things such as capacitors, resistors, or lightbulbs are commonly found in circuits.

There are three main types of circuits: a series circuit, a parallel circuit, and a combination circuit. Series circuits have only one pathway that the ions can flow, and are constructed with series connections, as seen below.

Parallel circuits, on the other hand, have multiple ways that ions can flow. In other words, each element in the circuit has its own positive track and negative track to run.

Combination circuits are what their name implies. They are simply a mix of both a series circuit and a parallel circuit.

Now we can talk about currents. Direct current has the ions always flowing in one constant direction, as opposed to alternating current. Alternating current has the ions constantly switching directions.

Electricity is a topic I have never really found difficult. At the age of eight I had been immersed in circuitry, forming different types of circuits in order to complete an objective. I suppose that alternating current has been a more difficult topic for me to grasp though; seeing as I have always dealt with direct current.

Looking at problems (we haven't actually covered electricity in my class), I noticed that even though it seems to be simple, you have to really know what you're doing, such as in the case of resistors, or else it's possible to get lost easily. Also, while looking at resistor problems, it seemed that in order to solve the problems, you had to know various laws and concepts well in order to arrive at the final answer, which is something I'm still not adept at in physics.


Currents can be seen at work every day. Anything that runs on batteries is generally using direct current. This includes a flashlight, your cell phone, and a laptop. Conversely, anything that plugs into the wall for power uses alternating current, such as a clothes washer or oven lights. There are also AC/DC converters so that an appliance that uses direct current can use alternating current, and vice versa.


Just because I really like the band AC/DC, here's Back in Black, considered to be one of the greatest songs of all time.

Back in Black

Sources:

BerkeleyPoint. "How to Wire a Circuit in Parallel?" How To Wire A Circuit "In Parallel"?. Berkeley Point, 2012. Web. 25 Apr. 2012. <http://www.berkeleypoint.com/learning/parallel_circuit.html>.

ComPadre. "Electric Current." What Is An Electric Circuit?. The Physics Classroom, 2012. Web. 25 Apr. 2012. <http://www.physicsclassroom.com/class/circuits/u9l2a.cfm>.

Dictionary.com. "Electricity." Electricity|Define Electricity At Dictionary.com. Dictionary.com, 2012. Web. 25 Apr. 2012. <http://dictionary.reference.com/browse/electricity?s=t>.

Kinematics Say What?

I've chosen 1D motion to apply my knowledge to. This Prezi will give the information necessary to understand the upcoming application.

1D Motion Prezi

Now that the concepts of 1D motion have been explained, it's time to begin the application of this knowledge. I will be applying 1D kinematics to how the runway length for jets is determined, as well as whether or not all jets have the same length runway and why they do or do not.

The first question asks how the runway length for jets is determined. To demonstrate this, I have found that a Boeing 747-400 takes 51 seconds to go from 0 m/s to 77.78 m/s. This information already gives you the initial velocity, final velocity, and time. The starting distance can also be assumed to be 0m. From here, you would use one of the kinematics equations to solve for distance, and that would be the length of the runway. Here's how you would solve this:

X=X0+1/2(V0+V)t

X=0+1/2(0+77.78)51

X=1/2(77.78)(51)

X=1983.39m

The second part of this question is whether or not all jets have the same runways, and why. Jets do not have the same runway length, and this is due to the differences in their acceleration. If a jet fails to reach the required takeoff speed, this can cause the plane to crash. Each runway is made for this purpose-- the plane can reach its takeoff speed and have room to lift off.

 

 

To explain how too short and too long a runway affects jets, I have created an Xtranormal video.

Sources:

"Acceleration of B-747-400." The Wings Of The Web. Airliners.net, n.d. Web. 11 Apr. 2012. <http://www.airliners.net/aviation-forums/general_aviation/read.main/1248698/>.

Kinematics Mayhem

Kinematics is defined as the branch of physics that concerns motion and its equations. Motion comes in 1D, 2D, and 3D, each having its own set of equations. In my physics class, we've studied 1D and 2D motion. The equations for 1D motion are:

• V= V0+at
• Vav=1/2(V+V0)
• X=X0+1/2(V0+V)t
• X=X0+V0t+1/2at²
• V²=V0²+2ax

2D motion has two components to it, an X-component and a Y-component. The X-component equations are:

• X=V0t
• Vx=V0x
• Vx² =V0x²

The Y-component equations are:

• Y=Y0+V0yt+1/2gt²
• Vy=V0y+gt
• Vy² =V0y² +2gy

What I find really difficult about this is the 2D kinematics equations, and knowing when to use which equation in order to find the horizontal or vertical component of the velocity. Understanding how to work problems that have a projectile curving has also been a struggle of mine.

My problem solving skills have major room for improvement... That being said, I feel as though I've done most everything I can to try and improve them, starting with practicing the problems on my own time, to receiving tutoring. My biggest weakness is in the reasoning and math, so I will start there and try to continue to build my (lack of) skills.

Now that I've given a brief introduction to kinematics, please enjoy a word find (courtesy of Discovery Education PuzzleMaker). 

In real life, kinematics can be applied to a sledder cruising down a hill (1D), or a person in the back of a pick-up truck shooting a pellet gun straight up in the air (2D).

Sources:

"Create Your Own Puzzles." Free Puzzlemaker. Discovery Channel, 2012. Web. 3 Apr. 2012. <http://www.discoveryeducation.com/free-puzzlemaker/?CFID=2924304&CFTOKEN=60942403>.

"The Kinematics Equations." The Physics Classroom. The Physics Classroom, 2012. Web. 3 Apr. 2012. <http://www.physicsclassroom.com/class/1dkin/u1l6a.cfm>.

"What Is Kinematics?" Physics-Online Info. Physics-Online Info, n.d. Web. 3 Apr. 2012. <http://www.physics-online.info/book1/chapt1/Topic1-4.htm>.