ch 20 #63

During one of Franklin’s initial experiments he noticed that a pith ball or cork would be repelled if touched together but at would be attracted to a charged object. He realized this because the two objects were initially charged differently, but once they touched they acquired the same charge. He later realized if he replaced the charged object with a bell he could make an "electric bell." Later he used the bell as a lightning detector that became known as Franklin’s Bells. When the bell was connected to a lightning rod it would ring when an electrical storm was nearby, which could be used as an early form of weather detection.

The Leyden Jar is a device that was invented by Pieter van Masschenbroek in 1975 to store electric charge. The Leyden Jar was made of a glass bottle with water to act as a conductor for electricity. It was made with a metal wire that passed through a cork which closed the jar. The design of the jar later added 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.

4/1/08 Blog Post

Heyy, so today we started off by Mr. Wirth reminding to scribes to always be alert! Well this one obviously was, because I remember that we started off with a review sheet he handed us...

We did about 4 problems on the sheet that reminded us of the properties of this unit.
We calculated the amount of charge passing through resistor (R2) in 60 seconds. We did this by using I=delta q/T
Next we learned how to draw a parallel circuit using the ammeter symbol, battery, and 2 resistors of a certain ohm.
Lastly we calculated the equivalence resistance of the circuit by using the equation 1/Req=1/R + 1/R2...

After reviewing these concepts we jumped right into notes...
VOLTMETER: measures potential difference between two points in a circuit.
**these are connected in PARALLEL
**extremely HIGH internal resistance
**draws extremely SMALL current

AMMETER: measures current through ONE point in a circuit...
**connected in SERIES
**extremely LOW internal resistance
**creates extremely SMALL voltage drop


so that was all the notes did for the day... by the way ellen missed all of this because she was not here. so i hope she takes full advantage of this blogging experience...

ok peaceout

Chapter 20 Question 63

Leyden Jar
It is a devide for storing electrical charge and was invented in 1745 Pieter van Musschenbroek. It was the first capacitor and was used to conduct experients dealing with electricity. the design consists of an electrode connected to a metal foil folding part on the inner surface of a glass jar. The conducting foil is wrapped around the outside of the jar which is charged by an electrostatis generator, which is connected to the inner electrode and the outter plate is grounded. Both the inner and outter surfaces of the jar hold opposite charges. Originally it was a glass bottle partially filled with water with a wire passing through the cork that closed it. Benjamin Frankilin found out the charge was stored in the glass and not the water.
Franklin's Bells
During one of his initial experiments he noticed that a pith ball or cork would be repelled if touched together but initially would be attracted to a charged object. he realized this because the two objects were initially charged differently, but once they touched they acquired the same charge. He later realized if he replaced the charged object with a bell he could make an "electric bell." Later he used the bell as a lightning detector. When the bell was connected to a lightning rod it would ring when an electrical storm was nearby.

March 25, 2007

Today we began a new unit called Electrical Circuits, which originated in about 1350-1400. A circuit is a closed loop or path along which charged particles move, in which an electrical current can exist. a cirsuit is formed by a source of potential differnce, including one or more resistances.

Circuit elements include:
Source elements: device or system that can produce a potential difference
Load elements: device or system to which the source is connected
Control elements: used to control the flow of electrical current
Path elements: used to interconnect other elements

Circuit symbols can be found on page 4 of the reference tables

Terms and Definitions:
Current (I)- flow of electric charge, the time-rate at which charge flows past a given point in a circuit.
Unit: ampere (A)
1 ampere= 1 coulomb/second 1A=1c/s
equation: I= the change in q/time

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.