http://www.johndyer.com/sparxarcs.html
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use the basic structure of an atom to explain
how objects become
ELECTRICALLY CHARGED
.
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explain CONSERVATION OF
CHARGE
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predict what
charge
will occur when two
insulators
are
physically rubbed together based on how well an
insulator
holds onto electrons.
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understand the differences between charging by
FRICTION
, INDUCTION,
CONDUCTION
and POLARIZATION.
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apply the definition of a
COULOMB
to find the
charge
on an electron or proton.
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use
COULOMB’S LAW
to calculate the
electrostatic force between two
charges
.
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-Bohr Model of an Atom
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-Bohr Model of an Atom
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Electron
Proton
Neutron
-Charge = “Negative”
Mass = 9.109 x 10
-31
kg
Charge = “Positive”
Mass = 1.672 x 10
-27
kg
= Zero net charge
= Zero net charge
6 Positive
6 Negative
6 Positive
6 Negative
Conservation of Charge
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--
-+
+
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+
+
+
= +2 net charge
4
8
= -2 net charge
-+
+
+ +
-4 Positive
3 Negative
= + 1
4 Positive
5 Negative
= - 1
+
+
+ +
-What is the charge on this Atom?
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There is a
repulsive force
between
electrons
,
or between
protons
.
There is an
attractive force
between
electrons
and
protons
.
HOW MUCH
FORCE?
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We first need to
define a certain
1 DOZEN eggs
12 eggs
1 REAM of paper
500 sheets
1 BUSHEL of apples
2152.42 cubic inches
(
42-48lbs of apples)
1 SCORE years
COULOMB
A whole heck of
a boophoo bunch
of charge
ONE COULOMB
of charge (+ or -)
Equals
6.24 x 10
18
charges
ONE COULOMB
of charge (+ or -)
Equals
6.24 x 10
18
charges
6,240,000,000,000,000,000 charges
The smallest unit of charge is
the charge of one electron or proton.
Fundamental Units
Distance - Meters
Mass - Kilograms
Time - Seconds
ELECTROSTATICS
Force
2 x Force
Radius
1 Coulomb
1 Coulomb
2 Coulombs
1 Coulomb
2 Coulombs
2 Coulombs
3 Coulombs
4 Coulombs
4 x Force
12 x Force
Distance = 1 2 3 4
Area = 1 4 9 16
Intensity = 1 1/
4
1/
9
1/
16
Intensity = 1 1/
2
2
1/
3
2
1/
4
2
Distance = 1 R 2 R 3 R 4 R
Force = 1 g 1/4 g 1/9 g 1/16 g
GRAVITY
FORCE = 1 N 1/4 N 1/9 N 1/16 N
ELECTROSTATIC FORCE
-
--
-
--
-
--
-
--
--
-
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FORCE
is
inversely proportional
to the square of the
distance
.
FORCE
is
directly proportional
to the product of the
charges
.
F
α
1
R
2
FORCE
is
inversely proportional
to the square of the
distance
.
FORCE
is
directly proportional
to the product of the
charges
.
F
α
q
1
·
q
2
R
2
Coulomb’s Law
F
= k
q
1
·
q
2
R
2
k = 8.9875 x 10
9
N·m
2
/ C
2
k ~ 9 x 10
9
N·m
2
/ C
2
F
α
q
1
·
q
2
F
α
1
F
g
= G
m
1
·
m
2
R
2
F
E
= k
q
1
·
q
2
R
2
Gravitational Force
Electrical Force
G = 6.67 x 10
-11
k = 8.9875 x 10
9
Very STRONG!
Very WEAK!
F
= Force (Newtons)
q
1
= charge on one object (coulombs)
q
2
= charge on the other object (coulombs)
-- ----
-
--
--
--
--How much
electrostatic
repulsive force
would there be
between these
two
charges
?
1.31 meters
F
= k
q
1
·
q
2
R
2
k = 8.9875 x 10
9
F = 22 Newtons
--
--
--
--
--
--
-
--
--
-- --
--
--
---
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-
--
How
far
would
these
charges
have to be apart
to have an
electrostatic
repulsive force of
1,000 Newtons
?
F
= k
q
1
·
q
2
R
2
k = 8.9875 x 10
9
R = .195 meters
- --
-
--
--
--
--.00025 Coulombs
.000017 Coulombs
? meters
--
--
--
--
--
--
-
--
--
-- --
--
--
---
-
-
--
r
hydrogen
=
5.31 x 10
-11
m
m
e
=
9.11 x 10
-31
kg
e
-
=
1.60 x 10
-19
C
v =
???
2,180,000 m/s
Charging by
Conductors & Insulators
Materials in which
charges are free
to
move about are called
conductors
.
Materials in which
charges are
not
free
to move about are called
Semiconductors
Semiconductors
are materials which
are good insulators in pure form, but
their
conducting properties can be
adjusted
over a wide range by
introducing very small amounts of
impurities.
Silicon, germanium, etc.
Superconductors
Superconductors
are materials that
lose all resistance
to charge
movement at temperatures near
absolute zero (0 K or about -273
o
C).
Recently, “high temperature” (above
Electrical
Conductor
Electrical
Insulator
http://www.made-in-china.com/image/2f0j00YMnECRgqqTbUM/Silicone-Rubber-Insulated-Wire-VDE-HO5S-K-.jpg
It is more difficult for electrons to travel
through the thin rubber coating than
it is for the electrons to travel
through many meters
of the metal.
http://www.standnes.no/chemix/periodictable/electrical-conductivity-table.gif
Copper
Silver
http://physicslearning.colorado.edu/pictures/5A10.10.jpg
Rubber Rod and Fur
Glass Rod and Silk
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-Rubber
is a better insulator than
fur
.
Silk
is a better insulator than
glass.
Rubber
Glass
Silk
Silk
Fur
http://www.phys.unt.edu/~klittler/demo_room/e&m_photos/pith_balls.JPG
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-http://www.physlink.com/estore/cart/item_images/886_xl.jpg
Electroscope
Gold
Leaf
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Clifton Bluhm Clifton Bluhm
Clifton Bluhm
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Charging by
POLARIZATION
F
= k
q
1
·
q
2
Electric Dipoles
•
An object that is electrically neutral overall, but
permanently polarized, is called an electric dipole.
https://sciencebasedlife.wordpress.com/2012/02/15/water-droplets-orbit-via-static-electricity-in-space-w-video/
