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PHYS 2212TEST 1 ReviewSpring '08
Chapter 21-Electric charge and electric field
Terms: Electric field, field lines.
Coulomb's law: Electric charges exert a force on each other
F k
Q1Q2
k
r2
1
40
Where F is force (N), r is distance (m), and Q is charge (C). F is repulsive for like charges and attractive for unlike
charges.
Unit of Charge: Coulombs (C). The charge on an electron is 1.6x10-19 C (There are 6.25 x1018 electrons in one
coulomb of charge).
Electric field: the force per unit charge that would act on a test charge q placed at a point where electric field is
defined.
E = F/q = kQ/r2 with the same direction of F.
Understand the contributions to the electric field due to multiple charges.
Understand the field lines.
Chapter 22- Gauss’s Law
Terms: electric flux, charge densities
Electric flux  E 
 
E
  da ;
Gauss’s Law
  Qin
E
  da 
0
Understand different charge distributions: charge per unit length, unit area, and unit volume.
Find the electric field for point charge, spherical charge, and cylindrical charge distribution.
Electric field = zero inside a conductor.
Chapter 23-Electric potential
Terms: Electric potential energy, electric potential, voltage
For two point charges:
U k
q1 q 2
r
Work done by the electric field, W = -U
b 

V   E  dl
a
Electric potential difference Vab: the work done to move 1 -C charge between the two points a and b; units: Volts
(1V = 1 J/C) => potential energy change PE= qVab.
For a uniform electric field E: Vab = Ed, where d is the distance between a and b.
Electric potential due to a point charge,
V k
Q
r
Chapter 24- Capacitance and dielectrics
Terms: Capacitance, energy density, dielectric constant
Capacitance: C = Q/V (= 0A/d for a parallel plate capacitor)
Capacitor in series: 1/C = 1/C1 + 1/C2 + 1/C3 + …..
Capacitor in parallel: C = C1 + C2 + C3 + …..
1
1
1 Q2
Energy stored in a capacitor: U  QV  CV 2 
2
2
2 C
Energy density u = 0E2/2
Dielectric constant K = C/C0