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Transcript
```Physics122
Exam #1
September 29, 2004
12:10 to 1:10 pm
Constants and equations for exam 1. You may detach this page if you wish.
________________________________________________________________________________
Coulumb’s Law constant
k=8.99 x109 N m2/C2
Permittivity of free space
0=8.85 x10-12 C2/N m2
Charge of one electron
-e=-1.60 x10-19 C
________________________________________________________________________________
Coulumb’s law
Electric field


Q1Q2
F  qE - definition of E
F k 2
r
Q
E  k 2 - point charge
r
E  V / d  capacitor, constant field
________________________________________________________________________________
Electric Potential
 
PE  qV - potential energy of a charge in electric field
V    Edr
Q
V
V
V
 potential of a point charge
Ex  
; Ey  
; Ez  
.
r
x
y
z
Work done by a electric force: W=-PEfinal-PEinitial)
Work done by external force to move a charge q in electric field: W=qVfinal-Vinitial)
________________________________________________________________________________
System of charges
 


dQ
E  E1  E 2  E3 .... - sum of point - like charges
E  k  2 - continuous distributi on of charge
r
dQ
V  V1  V2  V3  .....
V  k
r
________________________________________________________________________________
Electric Flux, Gauss’s Law

 
For unifrom field  E  E  A - electric flux; A  area vector, equal to area, pointing perpendicu lar to area
 
Q
 E   E  dA  E  0  outflux,  E  0  influx,
 E  , Q  enclosed charge
V k
0
________________________________________________________________________________
Trigonometry review
sin   (opp) /( hyp), cos  (adj ) /( hyp), tan   (opp) /( adj )
Pythagorean theorem: (hyp) 2  (opp) 2  (adj ) 2
________________________________________________________________________________

Vectors (A or A ) and Components (Ax, Ay)
A + B Nose to tail
– A points opposite A
A – B means A + (–B)
Component = (sign)(magnitude)(trig fn) C = A + B means C x  Ax  Bx and C y  Ay  B y
Magnitude of C = |C| =
C x2  C y2 Angle to nearest x-axis:   tan 1
1
| Cy |
| Cx |
Specify axis!
```
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