ElectrostaticsElectrostatics + + + - - -. Conservation of Charge Charge can neither be created nor destroyed Positive ions ---- fewer electrons than protons.

ElectrostaticsElectrostaticsElectrostaticsElectrostatics

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- -

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Conservation of ChargeConservation of ChargeConservation of ChargeConservation of ChargeCharge can neither be created nor destroyed

Positive ions ---- fewer electrons than protons

Negative ions ---- fewer protons than electrons

Electric Charge is measured in Coulombs6.3x1018 electrons make -1.0 C of charge6.3x1018 protons make +1.0 C of charge

Conservation of ChargeConservation of ChargeConservation of ChargeConservation of ChargeCharge can neither be created nor destroyed

rub electrons from a bar with furbar becomes positively charge by

the exact amount that fur becomes negatively charged.

bar becomes a tiny bit less massive

Coulomb’s LawCoulomb’s LawCoulomb’s LawCoulomb’s LawF k

q1q2

d2

The interaction force between two charges is:

directly proportional to the size of each charge (q1 and q2)andinversely proportional to the square of their separationdistance (d)

k= 9.0 x 109 N/m2/C2 Fe>>>Fg

Coulomb’s LawCoulomb’s LawCoulomb’s LawCoulomb’s LawF k

q1q2

d2

The interaction force between two charges is: directly proportional to the size of each charge (q1 and q2)

Double either q1 or q2 then F doubles.Double both then F quadruples

Coulomb’s LawCoulomb’s LawCoulomb’s LawCoulomb’s LawF k

q1q2

d2

The interaction force between two charges is:inversely proportional to the square of their separationdistance (d)

Double the separation distance then F is reduced to (1/4)Halve the separation distance then F is quadrupled (4x)

Coulomb’s LawCoulomb’s LawCoulomb’s LawCoulomb’s LawF k

q1q2

d2

The interaction force between two charges is:inversely proportional to the square of their separationdistance (d)

triple the separation distance then F is reduced to (1/9)(1/3) the speration distance then F is increased 9 fold (9x)

Coulomb’s LawCoulomb’s LawCoulomb’s LawCoulomb’s LawF k

q1q2

d2

The interaction force between two charges is:inversely proportional to the square of their separationdistance (d)

If separation distance is increased by 10 then F (Reduces/increases) by _________________

Coulomb’s LawCoulomb’s LawCoulomb’s LawCoulomb’s LawF k

q1q2

d2

As the charges above are released the force on each(increases or decreases)

+ +

Coulomb’s LawCoulomb’s LawCoulomb’s LawCoulomb’s LawF k

q1q2

d2

As the charges above are released the speed of each(increases or decreases)

+ +

Coulomb’s LawCoulomb’s LawCoulomb’s LawCoulomb’s LawF k

q1q2

d2

As the charges above are released the acceleration of each(increases or decreases)

+ +

Coulomb’s LawCoulomb’s LawCoulomb’s LawCoulomb’s LawF k

q1q2

d2

As the charges above are released the speed of eachincreases. Thus the green object has a __________charge. Positive, negative, can’t tell

? +

Coulomb’s LawCoulomb’s LawCoulomb’s LawCoulomb’s LawF k

q1q2

d2

As the charges above are released the force on eachincreases. Thus the green object has a __________charge. Positive, negative, can’t tell

? +

ConductorsConductorsConductorsConductors

Conductors have very loosely bound electrons. That is electrons that are not really attached to one particular nucleus. These electrons are sometimes called free electrons because they move freely when exposed to an electric field

GoldCopperSilverIonic solutions (salt water)

InsulatorsInsulatorsInsulatorsInsulators

Insulators have very tightly bound electrons. That is electrons that are firmly attached to one particular nucleus. These electrons are very hard to set in motion throughout the material

GlassDry woodPlastic

SemiconductorsSemiconductorsSemiconductorsSemiconductors

Semiconductors have moderately bound electrons. These electrons can be set into motion throughout the material when a moderately strong electric field is established in the material.

Carbon

Silicon

SuperconductorsSuperconductorsSuperconductorsSuperconductors

Superconductors have no electrical resistance to charge flow (infinite electrical conductivity)

Very cold silver (-269 °C)

ChargingChargingChargingCharging

Friction

Contact

Induction

Charge PolarizationCharge PolarizationCharge PolarizationCharge Polarization

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- - - - - -

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F

Electric FieldElectric FieldElectric FieldElectric Field

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E=F/q

q

Electric FieldElectric FieldElectric FieldElectric Field

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E=F/q

q

Electric FieldElectric FieldElectric FieldElectric FieldE=F/qorF=q E

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Uniform ElectricField betweentwo charged plates

+ qF

Electric Shielding Electric Shielding E=0 inside metalsE=0 inside metalsElectric Shielding Electric Shielding E=0 inside metalsE=0 inside metals

Electric Shielding Electric Shielding E=0 inside metalsE=0 inside metalsElectric Shielding Electric Shielding E=0 inside metalsE=0 inside metals

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Electric Potential (Volts)Electric Potential (Volts)Electric Potential (Volts)Electric Potential (Volts)Electric Potential energy (J) Charge (C)

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+ qFEP = EPE / q

Volt=Joule/Coulomb

Electric Potential energy = Work

Electric Potential (Volts)Electric Potential (Volts)Electric Potential (Volts)Electric Potential (Volts)Electric Potential energy (J) Charge (C)

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+ qFWhat is the electricpotential between two plates when it takes 2.0 J of work to move a 0.001 Ccharge from - to + plate?

Electric Potential energy (J) Charge (C)

What is the electric potential between two plates when it takes 2.0 J of work to move a 0.001 Ccharge from - to + plate?

Given: W=EPE=2.0 J Charge=0.001 C

Want: EPSolution: Electric Potential=

Electric Potential energy (J) Charge (C)=2.0 J/0.001 C = 2000 Volts

1 Volt=1J/C

Given: W=EPE=2.0 J Charge=0.001 CWant: EPSolution: Electric Potential=

Capacitors & Energy Capacitors & Energy StorageStorage

Capacitors & Energy Capacitors & Energy StorageStorage

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+ qF