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What’s Happ’nin?
By now you should have registered on WebAssign and tried the initial assignment.
Watch for the appearance of a REAL assignment.
You should be reading the first chapter.
You should have read the syllabus (web).
TRIBOELECTRIC SERIES
your handglass
your hairnylonwoolfursilk
papercotton
hard rubberpolyester
polyvinylchloride plastic
TRIBOELECTRIC SERIES
When we rub two different materials together, which becomes positively charged and which becomes negative? Scientists have ranked materials in order of their ability to hold or give up electrons. This ranking is called the triboelectric series. A list of some common materials is shown here. Under ideal conditions, if two materials are rubbed together, the one higher on the list should give up electrons and become positively charged. You can experiment with things on this list for yourself .
GI V
ES
UP
MO
RE
EL
EC
TR
ON
S
+
-
Pith Main Entry: 1pith Pronunciation: 'pithFunction: nounEtymology: Middle English, from Old English pitha; akin to Middle Dutch & Middle Low German pit pith, pit1 a : a usually continuous central strand of spongy tissue in the stems of most vascular plants that probably functions chiefly in storage b : any of various loose spongy plant tissues that resemble true pith c : the soft or spongy interior of a part of the body
How many ways can we transfer charge? Let us count the ways.
……………..Willie the Shake
Direct Contact Separation of bonds
(rubbing, etc,) Conduction Induction Magic.
Coulomb’s Law
F is a vector. magnitude direction
1/40=k=8.99 x 109 Nm2/C2
DEFINITION – Unit of Charge is the coulomb
221
04
1
r
F
Let’s Do Some Problems
Strategy1. Think about how you will proceed.
2. What information is given, what is missing?
3. Develop the equations in an algebraic format.
4. Solve for an algebraic solution.
5. Plug in the numbers at the end.
6. Look at some special cases to check on consistancy.
7. Think about what you have learned that is worth retaining.
In the figure, a central particle of charge -2q is surrounded by a square array of charged particles, separated by either distance d or d/2 along the perimeter of the square.
In the figure, particle 1 of charge +1.0 µC and particle 2 of charge -4.0 µC, are held at separation L = 11.0 cm on an x axis. If particle 3 of unknown charge q3 is to be located such that the net electrostatic force on it from particles 1 and 2 is zero, what must be the coordinates of particle 3? x=[-11] cm y=[0] cm
What is this “charge” thing?
There are two charged particles we will be concerned with: Electrons Protons
Electrons have a charge of –e
Protons have a charge of +e ALL charges are an integral
multiple of this fundamental charge “e”
What have we found?
There are TWO types of charge. Positive Negative
Like Charges Attract Un-Like charges repel The force between charges
increases as they are brought closer together.
This charge separation results from chemical bonds which are severed in the process.