The Life of Period 1 Physics Class of March 13, 2008

White Board Review

Today started of as any other review day with the white board questions. Make sure you all know how to draw a single positive charge and a single negative charge. Also, know the pair of positive charges of equal magnitude, positive and negative charge of equal magnitude, as well as a positive and negative charge of different magnitudes. Some of these examples look as follows:

Ok now onto the new material:

Work

-Work is done when a force is appplied over a distance, the unit for work is the Joule. If we move a charge in an electric field, and the charge is repelled by the field, then we do work against the field. The potential energy of the charge is increased by the amount of work done

Electric Potential Difference/ "Potential Difference"

-Consider moving a charge "q" between 2 points A and B. the work we do is "W" and we have thus increased teh potential energy of q by "w" joules. So we have "Work Per Unit Charge" AKA a potential difference exists between points A and B.

Potential Difference is the change in electricl potential energy per unit charge as a charge is moved from one point to the other. V=W/q . . . . (don't worry the equation is on the reference tables) Also V= volts of potential difference

Electron- Volt/ "Amount of Work"
-The tiny amount of work from the previous promblem is defined as the "elecgtron-volt"
- Symbol is eV
Formal Definition
-The energy required to move one elementary charge (e) through a potential difference of one volt (v)

-Electron-Volt is also on the reference tables

Electric Potential
-Similar to the concept of gravitatonal potential
- we used mgh to calculate gravitational potential
- this implies a preference point whre h=0, so gravitational potential=0 at that point
- often we might use sea level as h=0 if the object does not move
-For elecric potential we use a distance of infinity from the charge in question
-Elecgtric potential is defined as a work per unit charge
-work required to birng one coulomb of positive charge in from infinity to a point in an electric field
-results in electric potential energy equal to the work done
-it is a scalar quantity
-unit is jouls/coulomb (j/c)




* BAGEL DAY COUNT-DOWN: 7 DAYS *

#63 Blog Post

The Leyden Jar was a device designed by Pieter van Masschenbroek in 1975 to store electric charge. Originally the Leyden Jar was made of a glass bottle filled a little bit with water to act as a conductor. The jar had a metal wire passing through a cork which closed the jar. At this time there was no outer plate. Later the design changed to a metal foil coating part of the inner surface and a conductor foil wrapped around the outside surface. The jar is also now charged by an electrostatic generator connected to the inner electrode, with the outer plate being grounded. Additionally, the inner and outer surfaces store opposite charges that are equal in amount.
The Wimshurst Machine, was designed between 1880 and 1883 by James Wimshurt to generate high voltages. The device consisted of two large contra-rotating discs, that are mounted in a vertical plane, two cross bars with metallic brushes, and a spark gap. This device creates electric charges through the concept of electrostatic induction. This works when the two insulated disks and the metal sectors rotate in opposite directions passing the crossed metal neutralizer bars and brushes, creating an imbalance of charges. The positive feedback increases the accumulated charges until the dielectric breakdown voltage of the air is reached which is what makes the sparks which jumps across the gap of the two disks.

#63 blog post

Static electricity has been involved in experiments since the 1700s. One of the first experiments with static electricity involved the Leyden Jar. The Leyden jar was invented in 1745 by Pieter van Musschenbroek. This was the first capacitor and were used to conduct experiments involving electricity. The original model was a glass bottle partially filled with water with a metal wire passing through the cork that was used to close the bottle. Another invention that was used for early static electricity experiments was the Wimshurst machine. The Wimshurst machine is an electrostatic device for generating high voltages developed between 1880 and 1883 by James Wimshurst. "It has a distinctive appearance with two large contra-rotating discs mounted in a vertical plane, two cross bars with metallic brushes, and a spark gap formed by two metal spheres." The device did not have the previous disadvantage to temporarily and randomly switch its polarity. Overall the static electricity within history has progressed over the years.

3/7/08 class

happy friday!!

we had our usual bagels for breakfast club brought in by me. Then we did a mini lab. We rubbed fur and silk on plastic and glass rods as well as a ruler. The point of this lab was to determine the charge on these various materials and how their charge changed.

After that we just chilled. the end.

Last Wednesday

Today we spent our time exploring the world of electricity. This post was the introductory day to electricity therefore we spent most of our time doing mini experiments.
We first demonstrated static electricity by rubbing a orange balloon on Austins head. (This balloon was later used on probably 15 students therefore i feel this experiment was highly unsanitary.)
We next demonstrated electricity by rubbing bunny fur to create a "magnetic" charge that would pick us crumbs.
By rubbing plastic and silk the plastic rod was able to pick up bits of paper.
The last experiment was showing how water bent because it was attracting to the certain charged rod.
These experiments demonstrated how opposites attract.

This concludes my blog post. This day was more about experiements that have to be seen rather than heard

PLEASE COMMENT ON THIS WONDERFUL POST!

Physics Explained

By Alex Eberts
Many people have a lot of unanswered questions regarding some of the things that we as humans see on a daily basis. Why do rainbows occur? How are mirages visible? Why is the sky blue? How come there are so many colors in a sunset? All of these questions can be answered using physics. Physics can explain many of the natural phenomenon’s we see everyday.


Glass can create different effects using visible light and the spectrum of colors. The effect glass creates when light is refracted is called dispersion. Dispersion occurs when the different colors, like blue and red, refract or bend in the glass in different ways. One specific device that has this effect is a prism; it breaks up the white light into all of the different colors. Raindrops act as prisms because if the sun is shining while it is raining then the light from the sun will refract or be dispersed off the raindrop. The white light hits the raindrop and when it is dispersed it is separated into different colors. This creates the effect of the rainbow and this is how we see rainbows. The diagram below demonstrates a raindrop acting as a prism with the white light from the sun being dispersed and refracted off it.











The raindrop acts like mirror also because it some of the dispersed light back at the sun. The different colors in the white light enter the raindrop at different angles therefore creating the different colors. Each raindrop only helps to contribute to one beam of light that is seen in the rainbow. Raindrops that are found located higher in the sky are red, orange or yellow light and raindrops that are found located lower in the sky are green, blue and violet. The antisolar line helps us to determine the color we will see. If a raindrop is located at 42° of the antisolar line then we will see red light. This helps to create the rainbow as a whole and make it so large. If the raindrop is located at 40° at the antisolar line then we will see blue light etc. The diagram below helps to explain how we see things due to the antisolar line. (Physics of Rainbows)











Why is the sky blue? Light in the sky is considered to be scattered light. This means that it is made up of many particles that when light is refracted or dispersed off of them it creates the blue sky that we see everyday. However, the sky is not only made up of blue light, it is made up of all the colors of the spectrum our eyes just mainly see blue. The image of clouds in the sky is created a fairly similar way. The reason why our eyes see white clouds is because it is light bouncing of water particles in the air. Therefore the clouds may look white and opaque, but they are really transparent.(Physics of the Blue Sky)

Sunsets and sunrises have the effect of being very colorful because of light scattering off of molecules located in the atmosphere. The spectrum of the color blue is much more readily visible to the human eye therefore that is why when we look at the sky we mainly see the color blue. At sunrise and sunset the light from the sun has a harder time getting through the atmosphere to our eyes therefore light is scattered towards the red end of the spectrum.(Why the Sky is Blue)

Mirages are another effect that can be explained due to physics. Mirages happen when there are two different temperature layers in the air. There is a hot layer of air and a cold layer of air. Because there are two layers there is a boundary between them which can refract light it creates an image. An example of when this can occur is on asphalt in the summer time.(Mirages1)

Works Cited

http://acept.la.asu.edu/PiN/rdg/rainbow/rainbow.shtml#top

http://acept.la.asu.edu/PiN/rdg/sky/sky.shtml

http://physics.bu.edu/~duffy/PY106/Eye.html

http://www.unmuseum.mus.pa.us/mirage.htm

Winter Break Blog: Rianbows, Mirages, Color of Sky

Physics Explained

Rainbows:

White light is a combination of many colors; a rainbow is when the white light has all of its colors separated. To form a rainbow the white light from the sun hits the raindrops and then reflects off the side of the raindrops and exits into your eyes. Each angle has a different distinct color.

Color of Sky:

The sky is scattered sunlight whose particles are smaller than the wavelength of the light. The sky is actually not only blue, it has many other colors in it as well; just the eye are the most sensitive to blue and not so much violet, and most of the light in the sky is violet and blue, therefore, creating the blue image in the sky. A further explanation as to why the sky is the color blue is because of the preferential scattering of short wavelength blue light compared to the scatter of long wavelength of red light, which is proportional with the gases in the atmosphere to the scattering of light by individual molecules (Rayleigh scattering).

Mirages:



The effect that two air levels at different temperatures is a mirage. Light can be refracted; considering there are two different temperatures of air and cold air is denser than hot air is. The specific type of mirage known as the oasis mirage happens when the air just about the ground is heated by the ground. A real example of this is when you believe to see the asphalt ground as water. This appears like this because the black color of the asphalt heats up the above air fast, which creates the refraction of the light from the sky. Light is refracted many times if there are numerous amounts of layers of different temperature air. As a result to this, natural objects can appear to look like city buildings. An example of this type of mirage is the Alaskan City Mirage.

Works Cited

"Light and Optics." Patterns in Nature 2000 March 3, 2008 http://acept.la.asu.edu/PiN/rdg/rainbow/rainbow.shtml#top.

"What Causes a Rainbow?." 2000 March 3, 2008 http://www.howstuffworks.com/question41.htm.

"Blue Skys and White Clouds." Patterns in Nature 1999 March 3, 2008 http://acept.la.asu.edu/PiN/rdg/sky/sky.shtml.

"Mirages in The Sky." 1998 March 3, 2008 .