Electrostatics the study of electrical charges at rest Electrodynamics the study of electrical charges in motion opposite Two opposite types of charge exist, named positivenegativeBenjamin Franklin positive and negative by Benjamin Franklin.Benjamin Franklin Benjamin Franklin Charge is a property of matter.

Charged particles exist in atoms. Electrons are responsible for negative charge; protons for positive charge; neutrons have no charge. Small amounts of ordinary matter contain incredible amounts of subatomic particles!

Conductor material that allows charges to move about easily Insulator material through which charges will not easily move Basic Law of Electrostatics Like charges repel; unlike charges attract Link link

Click here to view ahere simulation of the behavior of pith balls in the vicinity of charged rods. See a movie here.here

Click here to read about charging objects by friction. here View a simulation of charging a balloon by rubbing it on your hair and then sticking it to a neutral wall here. here Learn all about Ben Franklin and his work with electricity here. here

rodelectroscope charging a rod and electroscope positivelynegatively positively and negatively conduction induction by conduction and induction conduction When charging by conduction, touches the rod touches the electroscope. same charge The electroscope gets the same charge as the rod. induction does not When charging by induction, the rod does not touch touch the electroscope. The electroscope gets opposite charge the opposite charge of the rod.

Go here here, here, and here Go here, here, here, and here here to view simulations of charging an electroscope. Read more here. here

COULOMB’S LAW The force between two charged objects is directly proportional to the product of their charges and inversely proportional to their separation distance squared. link1link1, link2, link3, link4, link4link2link3link4

In equation form: F  F is the force of attraction, measured in NEWTONS, between charges q 1 and q 2 k k is the Universal Electrostatic Constant, equal to 9.00 x 10 9 N m 2 /coul 2 q1q1 q2q2 q 1 and q 2 are the attracting charges, measured in Coulombs d2d2 d is the distance between the charges, and is measured in METERS

The SI unit of charge is the Coulomb, named in honor of Charles Augustin Coulomb Charles Augustin Coulomb. Charles Augustin Coulomb 1 C = charge on 6.25 x electrons (or protons) 1 e - = 1.60 x 10  19 Coul = elementary charge Electric force is a vector and must be treated as such.

Electric Fields An electric field exists in a region if space if a charge placed in that region experiences an electric force. The magnitude of an electric field at any given point is defined to be the ratio of the force on a charge at that point to the amount of charge. E = F/Q Electric field strength has units of Newtons/Coulomb (N/C).

The direction of the electric field at any point is defined to be the same direction as the direction of force on a positive test charge placed in the region at that point. Field lines point away from positive and toward negative charges.

Click here to view a simulation here showing the magnitude and direction of the electric force on a test charge when placed near other charges. Click here to view a simulation of a here charged particle moving through a region occupied by other charges.

Electric Potential Difference the change in electric potential energy per unit charge V = W/QV = W/Q The SI unit of electric potential VOLT difference is the VOLT, named in Alessandro Volta Alessandro Volta honor of Alessandro Volta. Alessandro Volta One VOLT is the electric potential difference between two points when one Joule of work is done in moving one Coulomb of charge between the points.

electric cell - a device that converts one form of energy to electrical energy Chemical cells convert chemical energy into electrical energy. Chemical cells can be “wet” or “dry”.

Solar cells Solar cells convert light energy into electrical energy. generator A generator converts mechanical energy into electrical energy. battery battery - two or more cells connected in series or in parallel

the flow of charged particles charged particles ; can be positive or negative, but usually negative (electrons) through a conducting metal

Electric current is measured in Amperes, in honor of Andre Marie Ampere Andre Marie Ampere Andre Marie Ampere Andre Marie Ampere. One Ampere is the flow of one Coulomb of charge per second. 1 Amp = 1 Coulomb per second = 1 C/s 1 Amp = 1 Coulomb per second = 1 C/s IQt I = Q/t

Ammeter a device that measures current Voltmeter a device that measures electric potential difference

power = work/time = (work/charge). (charge/time) = electric potential difference. current P (Watts) = V (Volts). I (Amps)

Analogies of simple circuits are these links: Water circuit analogy link link Air flow link link Various link link Teaching with Analogies link1, link2 link1link2link1link2

Resistance determines the amount of current flow = the ratio of potential difference to current = the ratio of potential difference to current R= V I The SI unit of resistance is the Ohm  Ohm, , named Georg Simon Ohm Georg Simon Ohm in honor of Georg Simon Ohm.Georg Simon Ohm One Ohm One Ohm of resistance is the resistance one Volt such that one Volt of potential difference one Amp is needed to obtain a current of one Amp.

The resistance of a circuit element depends on: the length of the conductor 1. the length of the conductor as length increases, resistance increases proportionally the cross-sectional area of the conductor 2. the cross-sectional area of the conductor as area increases, resistance decreases proportionally the resistivity of the conductor 3. the resistivity of the conductor as resistivity increases, resistance increases proportionally

Resistivity The resistivity, , of a conductor is equal to the resistance of a wire 1 cm long and having a cross-sectional area of 1 cm 2. R R = resistance, measured in Ohms =   = resistivity, usually in units of   cm l l = length, measured in cm A A = cross-sectional area, measured in cm 2 Investigate resistivity here here

Ohm’s Law The ratio of potential difference to current is constant. If R = V/I is a constant value for a given resistor, then that resistor is said to obey Ohm’s Law. Click here and here to link to pages describing resistor here color codes.

Click here and here to run here simulations of Ohm’s Law. Many circuit elements do not obey Ohm’s Law. Resistors that get hot, like light bulbs and heating elements, do not keep a constant resistance. Resistance generally increases as objects become hotter.

Resistor Circuits Series 1. total resistance is the sum of the separate resistors separate resistors R T = R 1 + R 2 + R current is the same through each resistor I T = I 1 = I 2 = I 3 = total potential difference is the sum of each V T = V 1 + V 2 + V In other words, in a series circuit, resistance and voltage add, but current stays the same.

R1R1R1R1 R2R2R2R2 R3R3R3R3 E = 12 V RT =RT =RT =RT = VT =VT =VT =VT = IT =IT =IT =IT = R1R1R1R1 R2R2R2R2 R3R3R3R3 V,V PT =PT =PT =PT = R,I,A P,W

R1R1R1R1 R2R2R2R2 R3R3R3R3 E = 12 V R T = 15 Ω V T = 12 V I T = 0.80 A R1R1R1R1 R2R2R2R2 R3R3R3R3 V,V P T = 9.6 W R,I,A P,W

Parallel 1. reciprocal of the total resistance is the 1. reciprocal of the total resistance is the sum of the reciprocals of the separate sum of the reciprocals of the separate resistors resistors 1/R T = 1/R 1 + 1/R 2 +1/R total current is the sum of the current through each resistor through each resistor I T = I 1 + I 2 + I potential difference is the same across each resistor each resistor V T = V 1 = V 2 = V 3 =... In other words, in a parallel circuit, resistance adds as reciprocals, voltage stays the same, and current splits. In other words, in a parallel circuit, resistance adds as reciprocals, voltage stays the same, and current splits.

E = 12 V RT =RT =RT =RT = VT =VT =VT =VT = IT =IT =IT =IT = R1R1R1R1 R2R2R2R2 R3R3R3R3 R, V,VI, PT =PT =PT =PT = R3R3R3R3 R1R1R1R1 R2R2R2R2 P,W

E = 12 V R T = 3.42 Ω V T = 12 V I T = 3.50 A R1R1R1R1 R2R2R2R2 R3R3R3R3 R, V,VI, P T = 42 W R3R3R3R3 R1R1R1R1 R2R2R2R2 P,W

Go to link1, link2, link3, link4, link5, and link6 to view link1link2link3link4link5link6link1link2link3link4link5link6 pages and simulations examining Kirchhoff’s Loop and Junction Rules. Kirchhoff’s Rules Loop Rule: The sum of the potential differences around any closed circuit loop is zero. Junction Rule: The sum of the currents into any circuit junction is zero.

The sites linked here and here here (click on “Circuit here Construction Kit”) allow you to build and test your own series, parallel, and combination circuits. For a complete interactive tutorial on electricity and magnetism, go here. For a complete interactive tutorial on electricity and magnetism, go here.here