Unformatted text preview: ulomb s Law
Fe = ke Q1 Q2
r Magnitude 2 • The SI unit of charge is the Coulomb, C
• ke is called the Coulomb Constant
– ke = 8.9875 x 109 N.m2/C2 = 1/(4πεο)
– εο is the permittivity free space
– εο = 8.8542 x 1012 C2 / N.m2
Note the similarity to Newtons law of gravitation! Vector Nature of
Electric Forces
• In vector form,
Q1 Q2
ˆ
F12 = ke 2 r12
r
•
ˆ
– r12 is a unit vector
directed from q1 to q2 • The like charges
produce a repulsive
force between them Comparing Gravitation and Electrostatics
Gravitation
mass
force between
masses
Grav. acceleration
(or field) Electrostatics
m m1m2
FG = G 2
r
G=F/m charge
force between
charges
Electric field Q Q1Q2
FE = k 2
r
E= F
Q Force mg Force QE Work mgh Work QEd Potential Energy mgh Potential Energy QEd =
QV Vector Nature of
Electrical Forces
• The force on q1 is equal in magnitude and opposite in
direction to the force on q2
–
F12 = −F21
• With like signs for the charges, the product Q1Q2 is
positive and the force is repulsive
• With opposite signs...
View
Full
Document
This document was uploaded on 02/21/2014 for the course CHEM 110A 110a at UCLA.
 Winter '13

Click to edit the document details