Making "Connections" About Electricity

There are three different kinds of electric circuit connections: series, parallel, and series-parallel (complex) connections. The specific kind of circuit we used is called a DC (Direct Current) circuit. A DC circuit calls for a closed circuit of constant voltages, currents, and resistors and is energized by a generator, such as a battery. Using an online PhET Circuit Construction Kit, I constructed a virtual example of each type of connection. An important equation to remember throughout this presentation is that voltage is equal to the product of current and resistance (V = IR).

I first built a series connection using two light bulbs and a single battery for energy. A series connection is when resistors are connected along a single wire path so that all of the electrons from the battery flow continuously through that one path. The total current (flow of charge) is the same as the current in both the first and second light bulbs, because there is only one path for the current to travel along and therefore the current is never divided or changed due to separate pathways. The total voltage drop in a series circuit is equal to the sum of the voltage drops in the first and second light bulbs. The resistance in a series connection increases as you add more resistors, because with each resistor comes more resistance along the wire path. If either one of the bulbs was removed, the remaining bulb would not be lit. This would happen because by removing a bulb, the circuit would no longer be closed and the path would have a gap where the bulb once was. The current would have no way of reaching the remaining bulb.


The second connection I built was a parallel connection using the same elements as before: two light bulbs and a battery. A parallel connection is when each resistor in the circuit is connected on its own new path. The total current is equal to the sum of the currents in each resistor. Instead of having only one path for the current to travel along, there are three separate paths. The current splits between these three paths, which is why the sum of the current in each of these paths would add up to the total current. The total voltage drop is equivalent to the voltage drop in each resistor. This is because the voltage travels into each path at a voltage equivalent to the original voltage of the battery and there is an equal voltage drop in each resistor. The resistance in a parallel connection decreases as you add more resistors. If either of the bulbs was removed, the remaining bulb would remain lit and shine even brighter than originally. The circuit would still be closed, because removing one of the light bulbs only cuts off one of the two paths that the current could travel on. The current no longer divides itself because there is only one path available for travel, and therefore the remaining bulb shines brighter due to the increased current.


The final connection I built was a complex connection using the same single battery for power as before. My complex connection consisted of a series connection between a single light bulb and a parallel connection of two more light-bulbs. In order to solve for the total current for a complex connection such as this one, the total equivalent resistance of the entire circuit must be found first by adding the equivalent resistance of the parallel circuit to the equivalent resistance of the series circuit. Here is why we use this equation: as I stated earlier, this is a complex version of a series connection, which requires us to add the resistance of each light bulb along the path of the wire. The parallel connection is viewed as a single light bulb along said path, reasoned for by Kirchhoff's first law about the conservation of charge. His law states that the sum of the currents entering a junction (such as this parallel connection) is equal to the sum of the currents leaving that junction. In other words, the current travels through the parallel connection in the same unchanging way as in a light bulb - the only difference is that it splits itself between a group of new paths and then regroups at the end of the junction. Once the total equivalent resistance of the entire circuit has been found, it can be used to solve for the total current. Since this complex connection is just a complicated version of a series connection, the total voltage drop is equal to the sum of the voltage drops on the circuit. First, the voltage drop of the series resistor is solved for by multiplying the total current of the circuit by the lightbulb's resistance. We can derive from the total voltage drop equation that the voltage drop in the parallel connection is equal to the difference between the total voltage of the circuit and the voltage drop in the series resistor. From there, we can also figure out that the voltage drop in the parallel connection is equal to the voltage drop in each lightbulb in said connection. If the light bulb in series was unscrewed from the circuit, the remaining light bulbs from the parallel connection would immediately go out. This is because, as I mentioned before, the current would have no way of reaching the parallel connection if the light bulb it was in series with was unscrewed and the path was cut off. If either the light bulb at the bottom or at the top of the parallel connection was to be unscrewed, the remaining bulb in the parallel connection would form a normal series connection with the series bulb. This would happen because by removing one of the two parallel bulbs, we are breaking off one path and leaving the current only one possible path to travel on.

"Coasting" Through Physics

For our final physics project, our class was to construct a popular iPhone application-themed amusement park that demonstrated our cumulative knowledge of physics over the past school year. My team, Team 3, chose to build a Tiny Wings-themed paper rollercoaster. Unlike the real application, the track of our coaster sends the bird - represented by a marble - in a vertical direction to its goal: the nest. We changed the direction of the path of the bird because in order to display a fuller knowledge of physics, we included elements such as funnels and vertical loops. Raising the height of the ride allowed us to include more of these elements in our coaster. Two of the key elements of physics shown in our coaster are the transfer of energy from potential to kinetic and free-fall. Our Tiny Wings rollercoaster not only displays our knowledge of physics, but it is also a thrill for people of all ages. There is a small height limitation: the rider cannot be any bigger than a marble. Come and enjoy our ride today!

Tiny Wings Roller Coaster on Prezi

Testing Data and Specifications

Reflection off of Shutters

My photo is a natural photo of the sun's rays reflecting off of the shutters in front of a classroom window. The physics principle captured in this photograph is that of reflection, with a focus on the law of reflection.

In this photograph, the light rays are reflecting parallel to the ground and, because the shutters provide a smooth surface, they are going through regular reflection. Regular reflection is also illustrated and proven by looking at the reflected rays. The rays are not going in various directions; Rather, they are parallel to one-another. Also, this picture represents the law of reflection. The law of reflection states that the angle of incidence is equal to the angle of reflection. Although it may appear that the rays are cast at an angle of reflection which is much larger than the angle of incidence, the two angles are actually equal. The key is to look at the angle of the shutters. The rays arrive parallel to the front end of the shutters (the end closest to the window) and are reflected by said end of the shutters at an angle parallel to the angle of the shutters. In other words, both the angle of incidence and the angle of reflection are parallel angles to the surface, making them equal and following the law of reflection.

Do the Wave!

The electromagnetic spectrum represents the many types of radiation as a group. Radiation occurs when energy is released and travels in moving particles or waves. Electromagnetic waves are transverse waves that have amplitude, velocity, wavelength and frequency. In addition, these waves do not need a medium to travel through - they are able to travel by vacuum! These are the seven type of radiation, listed from lowest frequency and longest wavelength to highest frequency and shortest wavelength: radio, microwaves, infrared, visible, ultraviolet, X-rays and gamma rays. I am going to discuss two of these types of radiated waves in depth: radio waves and X-rays.

Radio waves have two main characteristics, directness and noise occurrence. The "directness" of a wave is how straightforward the wave is in reaching its target. A radio wave's directness depends on the frequency of the waves; if the frequency is higher, the radio waves' wavelength decreases and their directness increases. The "noise occurrence" of a radio wave is the occurrence of a noise produced when the radio wave has been interrupted by a medium. The delay between waves, which is caused by this medium, results in a static noise. The noise occurrence of a radio wave is present when the radio waves are weak, and the further the receiver is from the base which is emitting these waves, the weaker the waves are. The frequency of a radio wave varies from 3 kHz to 300 GHz, and their average wavelength is 1.5 x 10^3 meters. In the real world, radio waves are most frequently used for radio communication. For example, many people have radios either in their households or in their cars which are built to receive radio waves emitted by a antennae (shown in the picture above) from a single, non-portable base unit such as a radio station. These stations play music that then travels to the antennae of the portable radios.

X-rays are recognized by their velocity, wavelength, amplitude and frequency. The velocity of an x-ray in a vacuum is 186,000 miles/second, and its velocity is less when travelling through transparent matter. The wavelength of an x-ray is very short - an average of 10^-8 meters! An x-ray has amplitude equal to its intensity, and a frequency equal to its velocity divided by its wavelength. X-rays are commonly used in the real world for doctoring purposes. Doctors can take images of their patient's bones by using a special camera and film which capture images of trapped x-rays. This works perfectly for taking pictures of human bone because although x-rays can pass easily through soft human tissue, but have trouble passing through a hard material like bone.

Website Credits:

http://www.school-for-champions.com/science/emwaves.htm

http://en.wikipedia.org/wiki/Radio_frequency

http://en.wikipedia.org/wiki/Radio_waves#Discovery_and_utilization

http://www.school-for-champions.com/science/xray_characteristics.htm

http://panasonic.net/pcc/support/tel/cdl_noise.htm

http://pleatedjeans.files.wordpress.com/2010/06/homerx-old.jpg

Conservation of Energy

It's a basic fact for every being: When you work hard, you feel like you've lost energy. In this story, for example, Anita pulls a rubber band tightly and the energy she produces propels the rubber band across the room. We discovered where our energy goes and why it goes there in Unit V: Conservation Laws. To begin, there is one fact about energy that is critical to understanding the rest of the unit: Energy may be transferred in a multitude of ways, but the total amount of transferred energy is unchanged. In other words, the energy is conserved - hence the title of the unit, "Conservation Laws." There are three methods of energy transfer: Working, heating, and electromagnetic radiation. This rubber band situation focuses on the transformation of energy through working.

Mythbusters Lab

Our class recently embarked on a myth-busting adventure. Our goal was to try and disprove two myths, both of which appeared to be true. After testing each of these myths out with our self-created labs, my group discovered that these myths were, in fact, completely untrue!

Myth 1: An object always moves in the direction of the net force exerted on it.

If an object always moves in the direction of the net force exerted on it, and we roll a bowling ball across a level carpet surface with friction acting against the ball, then the bowling ball will continue to move in the same direction that it was originally traveling in.

For this experiment, we rolled a bowling ball across a carpet floor.




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If this myth were true, the bowling ball would've rolled in the direction of the net horizontal force acting on it: the force of friction. The force of friction is applying force to the left, yet the bowling ball continues to roll to the right. Therefore, this myth is false.

Myth 2: An object always changes its motion if there is a force exerted on it by other objects.

If an object always changes its motion if there is a force exerted on it by other objects and we swing a tennis ball into a bowling ball while in motion, the bowling ball's path/direction it is going in will not be affected.

Our procedure was as follows:
1. Suspend a tennis ball from the ceiling with a piece of string.
2. Hold the suspended tennis ball in the air.
3. Roll a bowling ball into the path of the suspended tennis ball.
4. Release the tennis ball from grasp, allowing it to swing directly into the oncoming bowling ball.







The applied force of the tennis ball, which moved to the left, was not strong enough to make an impact upon the motion of the bowling ball, which was moving to the right. This myth has been busted!

To conclude, our group busted both myths. Myth One appears believable because many people don't take into account that the object could be in motion and that the strength with which it was moving could be greater than the net force acting upon the object. Most people believe this myth because they only imagine objects at rest being impacted - for example, if someone were to push a resting pillow (PUN!) off of their bed, the pillow would move in the direction with which it was pushed. Myth Two is often believed because people assume that the object is going to be acted upon by a force greater than the object's original force. We disproved this statement by trying to impact a bowling ball's motion with a much-lighter tennis ball, which obviously failed. These myths? BUSTED.

Newton's Laws of Motion

In my most recent journey through physics, I learned about forces. There are six specific kinds of forces: Applied, normal, friction, tensional, air resistance, and gravitational force. I learned how to summarize the forces acting on an object in a free-body-diagram. You can use these diagrams to solve for the sum of the forces in the X or Y axis. Also, I know Newton's Laws of Motion, which further define the actions of said forces.
The first law states that an object at rest and an object in motion will most likely stay at rest and stay in motion, respectively. These objects will also maintain the same speed and direction until an unbalanced force acts upon them. For example, a cat falling from a building that has reached terminal velocity will most likely continue falling at said velocity until it is stopped and caught by a fireman.
The second law states that the acceleration of an object is identical to the net force of the object and inversely identical to the mass of said object. In other words, the heavier an object is, the faster it will accelerate. Imagine a pebble and a boulder being rolled down the same incline plane. The boulder will accelerate faster than the pebble, because it has a larger mass.
Finally, the third law states that when one object acts with a force upon another object, there will be an equal but opposite reaction force from the second object onto the first. One example of this is when a person slams their toe into a door (I just did so a few minutes ago!). The action of the toe slamming into the door receives the reaction force of the door slamming into the toe - by human definition, this reaction is called PAIN.
In addition, I now know how to use the equation Fg = mg to solve for an object's mass and weight. I just need to substitute the provided information into the equation and solve for the missing quantity.
I didn't find too many problems with this section; As a matter of fact, this has been my favorite unit so far! The only difficulty I found was when I tried to write a net force equation for a pulley system. I couldn't understand why only certain forces were included in the equation. I fixed this problem when I highlighted the direction of motion along my FBDs. By following this highlighted path, I was able to identify the forces I need in my net force equation. I also figured out that the forces that went along with the direction of motion were positive, and contradicting forces were negative. This method of highlighting made it much easier to write net force equations!