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)




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