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

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