# Electrostatics.

## Presentation on theme: "Electrostatics."— Presentation transcript:

Electrostatics

Electrostatics Fe >> Fg Electrostatic Force (Fe)
- Study of electricity at rest Electrostatic Force (Fe) Attractive OR Repulsive Fe = centripetal force keeping e- in orbit Opposite Charges Attract Like Charges Repel Fe >> Fg 99% empty space Electrons – loosely bound Conductors - allow electrons to flow freely (Low e- affinity) Protons & Neutrons – tightly bound in nucleus Nucleus – 99% of atoms mass Gold Atom - few valence electrons loosely bound

Insulators - do NOT allow electrons to flow freely
(High e- affinity)

Electrostatics - Atomic Structure Conductors Insulators

Detecting Charge: Charge Detecting Devices RULES
Describe Rutherfords findings in his famous Gold Foil Experiment.

3 Methods of Charging Separation of Charge Charging by Contact
Friction Conduction Induction by Grounding Outcome Outcome Outcome

Units of Charge: Negative Charge Positive Charge
Elementary Particles (e) => Coulombs (C) What is the charge in Coulombs for... a) -6e b) +3e Coulombs (C) => Elementary Particles (e) How many extra/fewer e- does object have with charge of... a) -3.2 X10-19C b) 2.0 X10-19C ELECTRON CANNOT BE CUT INTO PIECES!!

Conservation of Charge & Charge Transfer:
2 metal spheres touch then separate… A B What is the charge on each sphere after contact? 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? +4e BEFORE -6e Total Charge = What if? A B AFTER Total Charge =

Multistep Charge Transfer
MicroCoulomb (μC) : a) How many elementary particles? b) How many MicroCoulombs? -5 μC x 1012e Analogy: 325cents. How many Quarters? Analogy: 636eggs. How many dozen? Multistep Charge Transfer Two spheres have charges of +3µC and +7µC respectively... What is the charge on each sphere after contact? How much charge was transferred in.. µC C e q 1. Net Charge = Δq= Δq= 2. Net Charge = 3. Net Charge =

Two 1kg charged objects with charges of +2C and -4C are .5m apart…
Coulombs Law: Two 1kg charged objects with charges of +2C and -4C are .5m apart… What is the electrostatic force (Fe) between the objects? What would be force if charges were +2C and +4C? c) What is the gravitational force (Fg) between the objects? Inverse Square Law Relationships a) 4r b) 2q1 c) 2q1, 3q2 d) 3q1, 3q2, 3r Fe Fe Fe Fe

Electric Field - E-Field Intensity/Strength
Electric Field Lines E-Field vs. G-Field Direction: Rules: What is the electric field strength if a point charge of 2C feels an attractive force of 10N? Given the field strength in part ‘a’, how much force would a proton feels in this field? If the sphere and the point charge are .1m apart, what must be the charge on the sphere?