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 positively

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 5/31/2005

Physics Electric Charge and Energy Models Rough Draft

Edington rough draft 5/31/2005

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 6.24 * 1018 charges A alternating current ammeter Amperes Amps anions battery battery capacitor cations circuit closed circuit closed loop conductor continuous conducting path continuous conducting path conventional current Coulombs Coulombs/sec direct current drift velocity Eelec electric current electric field electric potential electric potential energy electrical ground electromagnetic energy electromagnetic radiation electromotive force electrons electrons em radiation emf equivalent resistance filament hand rule I insulator ions ions Joules/coulomb linear device magnetic field mobile charge carriers mobile charged particles negative current flow net charge nonlinear device Ohms Ohm’s Law open circuit open loop p.d. parallel circuit positive current flow potential difference power protons R radiant energy resinous charge series circuit short circuit V vitreous charge voltage voltaic cell voltmeter Volts watts

New Math Models Rtot = R1 + R2 + … 1/Rtot = 1/R1 + 1/R2 + … V=RI linear devices: R constant P=IV