Electrostatics Lecture

• Properties of Electric Charges
• Electric Charge in the Atom
• Static Electricity, Charge, and the Conservation of Charge
Overview
Electric Charge and Field > Overview
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Lightning
Lightning is a dramatic natural example of static discharge.
Wikimedia. CC BY-SA http://upload.wikimedia.org/wikipedia/commons/thumb/4/44/Lightning_strike_jan_2007.jpg/800px-Lightning_strike_jan_2007.jpg View on
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Electric Charge and Field

• Charge is measured in Coulombs (C), which represent 6.242×1018 e, where e is
the charge of a proton.Charges can be positive or negative, and as such a
singular proton has a charge of 1.602×10−19 C, while an electron has a charge of -
1.602×10−19 C.
• Electric charge, like mass, is conserved.
Properties of Electric Charges
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Coulomb's Law
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• An elementary charge -- that of a proton or electron -- is approximately equal to
1.6×10-19 Coulombs.
• Unlike protons, electrons can move from atom to atom.If an atom has an equal
number of protons and electrons, its net charge is 0.If it gains an extra electron, it
becomes negatively charged and is known as an anion.If it loses an electron, it
becomes positively charged and is known as a cation.
Electric Charge in the Atom
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Planetary Model of an Atom

Static Electricity in a Slide
Friction between the girl's hair and the slide results in a transfer of electrons, which causes the hair and slide to be attracted to one another.
Wikipedia. "Static on the playground (48616367)." CC BY-SA http://en.wikipedia.org/wiki/File:Static_on_the_playground_(48616367).jpg View on Boundless.com

Charge Repulsion and Attraction
Charges of like sign (positive and positive, or negative and negative) will repel each other, whereas charges of opposite sign (positive and negative) will
attract each other.
Wikimedia. CC BY-SA http://upload.wikimedia.org/wikipedia/commons/thumb/d/de/Charges_repulsion_attraction.svg/364px-Charges_repulsion_attraction.svg.png

Coulomb's Law
• Provides a way of exactly calculating the force that charges exert on each other
• q1 and q2 are the magnitudes of the charges (in Coulombs).
• K is Coulomb’s constant. K = 8.99 x 109 kg m3 s-1 C-2.
• R is the distance between the two charges.
Wikipedia. "Coulombslaw." CC BY-SA http://en.wikipedia.org/wiki/File:Coulombslaw.svg View on Boundless.com
r
F =
Kq1q2
r2

Coulomb's Law – Simplified for Chemistry 11
• The electrostatic force between two charges is…
• Stronger if the product of the charges is larger
• Stronger if the charges are closer together.
• For most applications we will not need to use Coulomb’s law to calculate the exact magnitude of the
force.
Wikipedia. "Coulombslaw." CC BY-SA http://en.wikipedia.org/wiki/File:Coulombslaw.svg View on Boundless.com
r
F =
Kq1q2
r2

the massive, positively charged central part of an atom, made up
of protons and neutrons
A) atomic spectra
B) nucleus
C) radioactive decay
D) nuclide

Wiktionary. "nucleus." CC BY-SA 3.0 http://en.wiktionary.org/wiki/nucleus
the massive, positively charged central part of an atom, made up
of protons and neutrons
A) atomic spectra
B) nucleus
C) radioactive decay
D) nuclide

The atom's net charge is determined by the number of
A) negatively charged electrons and positively charged photons
B) positively charged electrons and negatively charged protons
C) negatively charged electrons and positively charged protons
D) neutrons

Boundless - LO. "Boundless." CC BY-SA 3.0 http://www.boundless.com/
The atom's net charge is determined by the number of
A) negatively charged electrons and positively charged photons
B) positively charged electrons and negatively charged protons
C) negatively charged electrons and positively charged protons
D) neutrons

An elementary charge - that of a proton or electron - is
approximately equal to
A) 1.6×1019 Coulombs
B) 1.6×10-19 Coulombs
C) 1.6 Coulombs
D) 1 Coulomb

The SI of electric charge is
A) Ampere
B) Volt
C) Coulomb
D) Ohm

Electric charge in a closed system
A) can be created or destroyed
B) can be created but can not be destroyed
C) can not be created or destroyed
D) can not be be created but can be destroyed

Charge separation can be created by
A) friction
B) all of these answers
C) pressure
D) heat

Charge separation can occur because electrons are
A) negatively charged
B) massless
C) labile
D) can not be transferred from atom to atom

Wiktionary. "static electricity." CC BY-SA 3.0 http://en.wiktionary.org/wiki/static+electricity
an electric charge that has built up on an insulated body, often
due to friction
A) nucleus electrcity
B) voltage
C) static electricity
D) discharge electricity

an electric charge that has built up on an insulated body, often
due to friction
A) nucleus electrcity
B) voltage
C) static electricity
D) discharge electricity

Electric charge is a physical property of matter created by an
imbalance in the number of
A) photons and electrons in a substance
B) protons and neutrons in a substance
C) protons and electrons in a substance
D) atoms in a substance

Key terms
• conductor A material which contains movable electric charges. (CC BY-SA 3.0)
• coulomb In the International System of Units, the derived unit of electric charge; the amount of electric charge carried by a
current of 1 ampere flowing for 1 second.Symbol: C (CC BY-SA 3.0)
• dielectric An electrically insulating or nonconducting material considered for its electric susceptibility (i.e., its property of
polarization when exposed to an external electric field). (CC BY-SA 3.0)
• dipole moment The vector product of the charge on either pole of a dipole and the distance separating them. (CC BY-SA 3.0)
• discharge the act of releasing an accumulated charge (CC BY-SA 3.0)
• discharge the act of releasing an accumulated charge (CC BY-SA 3.0)
• electric charge A quantum number that determines the electromagnetic interactions of some subatomic particles; by
convention, the electron has an electric charge of -1 and the proton +1, and quarks have fractional charge. (CC BY-SA 3.0)
• electric field A region of space around a charged particle, or between two voltages; it exerts a force on charged objects in its
vicinity. (CC BY-SA 3.0)
• electric field A region of space around a charged particle, or between two voltages; it exerts a force on charged objects in its
vicinity. (CC BY-SA 3.0)
• gravity Resultant force on Earth's surface, of the attraction by the Earth's masses, and the centrifugal pseudo-force caused by
the Earth's rotation. (CC BY-SA 3.0)
• insulator A substance that does not transmit heat (thermal insulator), sound (acoustic insulator) or electricity (electrical
insulator). (CC BY-SA 3.0)
• insulator A substance that does not transmit heat (thermal insulator), sound (acoustic insulator) or electricity (electrical
insulator). (CC BY-SA 3.0)

• nucleus the massive, positively charged central part of an atom, made up of protons and neutrons (CC BY-SA 3.0)
• nucleus the massive, positively charged central part of an atom, made up of protons and neutrons (CC BY-SA 3.0)
• resistivity In general, the resistance to electric current of a material; in particular, the degree to which a material resists the flow
of electricity. (CC BY-SA 3.0)
• static electricity an electric charge that has built up on an insulated body, often due to friction (CC BY-SA 3.0)
• static electricity an electric charge that has built up on an insulated body, often due to friction (CC BY-SA 3.0)
• terminal velocity The speed at which an object in free-fall and not in a vacuum ceases to accelerate downwards because the
force of gravity is equal and opposite to the drag force acting against it. (CC BY-SA 3.0)
• voltage The amount of electrostatic potential between two points in space. (CC BY-SA 3.0)

Electrostatics Lecture

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