2The History of Electrostatics Electricity has been studied since the GreeksBenjamin Franklin made 1st major scientific contributions about electricity.
3Benjamin Franklin Ben proved that lightning is “static electricity” Imagined electricity as type of invisible fluid present in all matter.When matter contained too little, it was “negatively” charged.When it had an excess, it was “positively” charged
4What is an electric charge? Electric charges exist w/in atoms.Atom Neutral+ charge (protons) = -charge (electrons)Transferring electrons cause an atom to gain/lose chargeLike charges repel, opposite charges attract.
5SI measurement for electric charge Subatomic ParticlesType of ParticleCharge (in C)Mass (Kg)Proton+1.6 x1.67x10-27Electron-1.6 x9.11x10-31NeutronSI measurement for electric chargeC => Coulomb
6Conservation of Charge Charge is not created nor destroyed, it is only transferred from one object to another. *+ and - charges are separated through a transfer of electrons.*Compare this to The Laws of Conservation of Momentum, Matter, and Mass.
7Conductors and Insulators Electric insulatorA material in which a charge does not move easily.Glass, dry wood, most plastics, cloth, and dry air are all good insulators.Electric conductorA material through which a charge will move easilyMetals are good conductors because at least one electron from each atom can easily be removed.
83 Ways to Charge an Object FrictionConduction or contactInductionThe Law of Conservation of Charge states that even after an object is charged, the combined total charge remains the same.
9Charging by Friction2 neutral objects are rubbed together, each can become charged.Electrons are transferred from the balloon to the hair.
13Charging by Induction• Charging an object without touching it – A charged object is needed to charge an object by induction. – There is never any contact made between the charged object and the object being charged. – Only conductors can be charged by the induction.
17Coulomb’s Law Electric Static Force Equation Fe= K q1q2 / r2 • UNITS – Charge (q) measured in coulombs (C)Proton charge xElectron charge -1.6 x– Distance (r) measured in meters– Force (F) in Newtons– Coulomb’s Constant (K) = × 109 N·m2/C2• Although Force is a vector quantity, Coulomb’s law does NOT give a direction
18Similarities Between Coulomb’s Law and Newton’s Law of Universal Gravitation
19Similarities and Differences Between Coulomb’s Law and Newton’s Law of Universal Gravitation Both are inverse square laws, the magnitude of the force is dependent on the distance between the two objectsNewton’s constant is much smaller than Coulomb’s, oftentimes the electrostatic force is much larger than gravitational force.Gravitational force affects objects over greater distances; electrostatic force is released before it grows too large.