Presentation on theme: "Electrostatics Electrostatics - Study of electricity at rest Electrostatic Force (F e ) Attractive OR Repulsive 1)Opposite Charges Attract 2)Like Charges."— Presentation transcript:
Electrostatics - Study of electricity at rest Electrostatic Force (F e ) Attractive OR Repulsive 1)Opposite Charges Attract 2)Like Charges Repel Conductors - allow electrons to flow freely (Low e - affinity) F e = centripetal force keeping e - in orbit F e >> F g Fe >> Fg 99% empty space Electrons – loosely bound Protons & Neutrons – tightly bound in nucleus Nucleus – 99% of atoms mass
Insulators - do NOT allow electrons to flow freely (High e - affinity) (High e - affinity)
Detecting Charge: Charge Detecting Devices Describe Rutherfords findings in his famous Gold Foil Experiment. RULES
3 Methods of Charging Separation of ChargeCharging by Contact Friction ConductionInduction by Grounding Friction ConductionInduction by Grounding Outcome Outcome Outcome
Units of Charge: Negative ChargePositive Charge Negative Charge Positive Charge Elementary Particles (e) => Coulombs (C) Elementary Particles (e) => Coulombs (C) What is the charge in Coulombs for... a) -6e a) -6e b) +3e b) +3e Coulombs (C) => Elementary Particles (e) Coulombs (C) => Elementary Particles (e) How many extra/fewer e - does object have with charge of... a) -3.2 X C a) -3.2 X C b) 2.0 X C b) 2.0 X C ELECTRON CANNOT BE CUT INTO PIECES!!
Conservation of Charge & Charge Transfer: 2 metal spheres touch then separate… Total Charge = AB AB BEFORE AFTER a)What is the charge on each sphere after contact? b)What subatomic particle(s) were transferred? From where to where? c) How much charge did A gain in elementary particles and Coulombs? d)How much charge did B lose in elementary particles and Coulombs? What if?
MicroCoulomb (μC) : a) How many elementary particles? b) How many MicroCoulombs? -5 μC 3 x e -5 μC 3 x e Analogy: 325cents. How many Quarters? Analogy: 636eggs. How many dozen? Multistep Charge Transfer Net Charge = q 0 0 Net Charge = Two spheres have charges of +3µC and +7µC respectively... a)What is the charge on each sphere after contact? b)How much charge was transferred in.. i) µC ii) C iii) e Δq=
Coulombs Law: Two 1kg charged objects with charges of +2C and -4C are.5m apart… a)What is the electrostatic force (F e ) between the objects? b)What would be force if charges were +2C and +4C? c)What is the gravitational force (F g ) between the objects? Inverse Square LawRelationships a) 4r b) 2q 1 c) 2q 1, 3q 2 d) 3q 1, 3q 2, 3r FeFe FeFe FeFe FeFe
Electric Field -E-Field Intensity/Strength Electric Field Lines Direction:Rules: E-Field vs. G-Field a)What is the electric field strength if a point charge of 2C feels an attractive force of 10N? b)Given the field strength in part a, how much force would a proton feels in this field? c)If the sphere and the point charge are.1m apart, what must be the charge on the sphere?