Physics
Electric Charge and Energy Models
Rough Draft
New Enduring Understandings
A. Substances are made of electrically charged particles.
B. Only two types of electric charge have been identified: resinous and vitreous.
C. Ben Franklin called these positive (+) and negative (-) since he thought that resinous charge was
an excess of “electric fluid” and vitreous was a lack of “electric fluid.”
D. If an object has more negative particles than positive particles, we say the object is negatively
charged. If the object has fewer negative particles than positive particles, we say the object is
positively charged. If an object has an equal number of negative particles and positive particles,
we say the object is electrically neutral.
E. Electric potential energy is carried by mobile charged particles.
F. Depending on the substance, the charged particles that are mobile within the substance may be
positively charged particles, negatively charged particles, or both types.
G. Conventional current flow is a model that assumes the electric energy is carried by positively
charged mobile particles.
H. Given a large enough electric potential energy difference, any substance will exhibit movement of
charged particles.
I. Electric energy is transmitted through a substance faster than the actual movement of the mobile
charged particles. This can be explained using a wave model of energy transport.
J. As mobile charged particles travel through a voltaic cell, chemical energy is transformed into
electric potential energy.
K. As mobile charged particles travel through a light bulb, the electric potential energy they are
carrying is transformed into light energy (electromagnetic energy) and thermal energy.
L. When more than one light bulb is included in a circuit, electric energy carried by the charge
particles is transformed into light energy and thermal energy at each bulb.
M. Moving charged particles interact with magnetic compass needles. We say that the moving
charged particles create a magnetic field.
N. The compass deflection direction indicates the charged particle movement direction.
O. The compass deflection magnitude indicates the number of charged particles passing by each
second.
P. The compass does not indicate the electric potential energy carried by the charged particles.
Q. A long-range force is exerted on a magnet by moving electric charges; a long-range force is
exerted on moving electric charges by a magnet.
R. The direction of the force on a magnet by a moving charge can be communicated by a hand rule.
Likewise, the direction of the force on a moving charge by a magnet can be communicated with a
hand rule.
S. A capacitor is a device that stores electrically energized charged particles.
T. A capacitor is composed of two conducting plates separated by an insulator.
U. Devices that transform electric potential energy into other energy forms are said to have an
electrical resistance.
V. Our simplest electric circuit model assumes that the connecting wires have zero electrical
resistance.
W. The quantity of electric charge traveling past a point in an electrical circuit each second is called
the electric current, I.
X. The electric potential energy difference between two points in a circuit is called the voltage, V.
Y. For a particular device, the ratio of electric potential energy difference vs. electric current is
defined as electrical resistance, R. A device exhibiting a constant ratio for all values of electric
potential energy difference and electric current is called a linear device. The mathematical model
for a linear device’s electrical behavior is V=RI where R is a constant.
Z. Complex circuits can be analyzed by simplifying them into equivalent series and parallel circuits
and using energy conservation and electric charge conservation concepts.
Edington rough draft 6/7/2005
Physics
Electric Charge and Energy Models
Rough Draft
History
A. Michael Faraday originated the electric fields and field lines physical model.
B. Charles Coulomb found the mathematical model that the describes the relationship between the force
on one charged particle by another, each particle’s charge, and the particles’ separation distance. This
mathematical model is an inverse square law, similar to the gravitational inverse square law.
C. James Clerk Maxwell created mathematical models that describe Faraday’s field models.
D. Benjamin Franklin originated the law of conservation of electric charge and gave us the common + and
- usage.
New Terms and Symbols
Ω
alternating current
Amps
battery
circuit
conductor
conventional current
direct current
electric current
electric potential energy
electromagnetic radiation
electrons
equivalent resistance
I
ions
magnetic field
negative current flow
Ohms
open loop
positive current flow
protons
resinous charge
V
voltaic cell
watts
New Math Models
Rtot = R1 + R2 + …
1/Rtot = 1/R1 + 1/R2 + …
V=RI linear devices: R constant
P=IV
Edington rough draft 6/7/2005
6.24 * 1018 charges
ammeter
anions
capacitor
closed circuit
continuous conducting path
Coulombs
drift velocity
electric field
electrical ground
electromotive force
em radiation
filament
insulator
Joules/coulomb
mobile charge carriers
net charge
Ohm’s Law
p.d.
potential difference
R
series circuit
vitreous charge
voltmeter
A
Amperes
battery
cations
closed loop
continuous conducting path
Coulombs/sec
Eelec
electric potential
electromagnetic energy
electrons
emf
hand rule
ions
linear device
mobile charged particles
nonlinear device
open circuit
parallel circuit
power
radiant energy
short circuit
voltage
Volts