Electrostatics
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Electrostatics. +. +. -. -. -. +. Conservation of Charge. Charge can neither be created nor destroyed. Positive ions ---- fewer electrons than protons. Negative ions ---- fewer protons than electrons. Electric Charge is measured in Coulombs

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Presentation Transcript
Electrostatics
Electrostatics

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Conservation of charge
Conservation of Charge

Charge can neither be created nor destroyed

Positive ions ---- fewer electrons than protons

Negative ions ---- fewer protons than electrons

Electric Charge is measured in Coulombs

6.3x1018 electrons make -1.0 C of charge

6.3x1018 protons make +1.0 C of charge


Conservation of charge1
Conservation of Charge

Charge can neither be created nor destroyed

rub electrons from a bar with fur

bar becomes positively charge by

the exact amount that fur becomes

negatively charged.

bar becomes a tiny bit less massive


Coulomb s law
Coulomb’s Law

The interaction force between two charges is:

directly proportional to the size of each charge (q1 and q2)

and

inversely proportional to the square of their separation

distance (d)

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


Coulomb s law1
Coulomb’s Law

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 law2
Coulomb’s Law

The interaction force between two charges is:

inversely proportional to the square of their separation

distance (d)

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

Halve the separation distance then F is quadrupled (4x)


Coulomb s law3
Coulomb’s Law

The interaction force between two charges is:

inversely proportional to the square of their separation

distance (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 law4
Coulomb’s Law

The interaction force between two charges is:

inversely proportional to the square of their separation

distance (d)

If separation distance is increased by 10 then F

(Reduces/increases) by _________________


Coulomb s law5
Coulomb’s Law

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As the charges above are released the force on each

(increases or decreases)


Coulomb s law6
Coulomb’s Law

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As the charges above are released the speed of each

(increases or decreases)


Coulomb s law7
Coulomb’s Law

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As the charges above are released the acceleration of each

(increases or decreases)


Coulomb s law8
Coulomb’s Law

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As the charges above are released the speed of each

increases. Thus the green object has a __________

charge. Positive, negative, can’t tell


Coulomb s law9
Coulomb’s Law

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As the charges above are released the force on each

increases. Thus the green object has a __________

charge. Positive, negative, can’t tell


Conductors
Conductors

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

Gold

Copper

Silver

Ionic solutions (salt water)


Insulators
Insulators

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

Glass

Dry wood

Plastic


Semiconductors
Semiconductors

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


Superconductors
Superconductors

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

Very cold silver (-269 °C)


Charging
Charging

Friction

Contact

Induction


Charge polarization
Charge Polarization

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F


Electric field
Electric Field

E=F/q

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q

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Electric field1
Electric Field

E=F/q

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q


Electric field2
Electric Field

E=F/q

or

F=q E

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F

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Uniform Electric

Field between

two charged plates


Electric shielding e 0 inside metals
Electric Shielding E=0 inside metals


Electric shielding e 0 inside metals1
Electric Shielding E=0 inside metals

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Electric potential volts
Electric Potential (Volts)

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Electric Potential energy (J)

Charge (C)

EP = EPE / q

Volt=Joule/Coulomb

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q

Electric Potential Energy = Work

Electric Potential Energy = Charge x Volts

1 Joule= Coulomb x Volt



Electric potential volts1
Electric Potential (Volts)

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Electric Potential energy (J)

Charge (C)

F

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q

What is the electric

potential between two

plates when it takes 2.0 J

of work to move a 0.001 C

charge from - to + plate?


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: EP

Solution: Electric Potential=

Electric Potential energy (J)

Charge (C)


Given: W=EPE=2.0 J Charge=0.001 C takes 2.0 J of work to move a 0.001 Ccharge from - to + plate?

Want: EP

Solution: Electric Potential=

Electric Potential energy (J)

Charge (C)

=2.0 J/0.001 C = 2000 Volts

1 Volt=1J/C


Capacitors energy storage
Capacitors & Energy Storage takes 2.0 J of work to move a 0.001 Ccharge from - to + plate?

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