QUARTER
THREE :
ENERGY & ELECTRICITY
How do you
experience electricity?
Bell Ringer
•Using only the PVC, move the
soda can, but you cannot
touch the can with the PVC or
blow on the can.
•Explain how you did it.
STATIC ELECTRICITY
Static
Electricity
Electrostatics – the study of electric charges
that can be collected and held in one place.
Electrostatics – is the study of static
electricity.
Benjamin Franklin
Made many contributions to the study of
electricity.
Famous with his kite and lightning
experiment.
The Structure
of Matter
Matter –
anything that
occupies space
and has mass
Atom –
building block of
matter
Subatomic Particle
“Meh”
Subatomic Particle Sizes
Mass Comparison
Subatomic Particle
Proton
Neutron
Mass (kg)
-27
1.672 x 10 kg
-27
1.675 x 10 kg
Subatomic Particle – Mass Comparison
Mass Comparison
Subatomic Particle
Proton
Electron
Mass (kg)
-27
1.672 x 10 kg
-31
9.109 x 10 kg
Subatomic Particle – Mass Comparison
Subatomic Particle Locations
Review!
Charged vs Uncharged Objects
Charged (+/-)
Positively
Charged (+)
Possesses more
protons than
electrons
Negatively
Charged (-)
Possesses more
electrons than
protons
Uncharged
(0)
Equal numbers of
protons and
electrons
Question Check!
1. ____ are the charged parts of an atom.
a. Only electrons
b. Only protons
c. Neutrons only
d. Electrons and neutrons
e. Electrons and protons
f. Protons and neutrons
charged uncharged.
Identify the following particles as being
or
If charged, indicate whether they are charged positively or negatively.
(n = neutron, p = proton, e = electron)
Negatively Charged
There are 10 electrons and 9 protons. This results in an imbalance of charge.
With more electrons than protons, the particle is negatively charged.
charged uncharged.
Identify the following particles as being
or
If charged, indicate whether they are charged positively or negatively.
(n = neutron, p = proton, e = electron)
Uncharged
There are 11 electrons and 11 protons. This results in a balance of charge. This
particle is neutral or uncharged.
charged uncharged.
Identify the following particles as being
or
If charged, indicate whether they are charged positively or negatively.
(n = neutron, p = proton, e = electron)
Positively Charged
There are 18 electrons and 20 protons. This results in an imbalance of charge.
With more protons than electrons, the particle is positively charged.
TRUE OR FALSE
An object that is positively charged
contains all protons and no electrons.
TRUE OR FALSE
An object that is negatively charged
could contain only electrons with
no accompanying protons.
TRUE OR FALSE
An object that is electrically neutral
contains only neutrons.
Difference Between Insulators and
Conductors
INSULATOR
A material through which a charge will
NOT move easily.
Examples:
Glass, Plastics, Dry Wood
CONDUCTOR
A material that ALLOWS charges to
move about EASILY.
Examples:
Metals, Iron, Water
NEUTRAL
VS
CHARGED
OBJECTS
Charged vs Uncharged Objects
Charged (+/-)
Positively
Charged (+)
Possesses more
protons than
electrons
Negatively
Charged (-)
Possesses more
electrons than
protons
Uncharged
(0)
Equal numbers of
protons and
electrons
Coulomb (C) – is the SI standard unit
for charge.
The charge of a single electron (e-) is equal to
-19
-1.6 x 10 C
The charge of a single proton (p+) is equal to
-19
+1.6 x 10 C
An object would need an excess of
18
6.25 x 10 electrons to have a total charge of
-1 C.
An object with a shortage of
18
6.25 x 10 electrons to have a total charge of
+1 C.
Exercise!
Object
Number of excess
protons/electrons
Quantity of Charge
in Coulomb
Kind of Charge
A
1 x 106 excess
electrons
-1.6 x 10 -13 C
Negatively Charged
B
3.5 x 108 excess
protons
5.6 x 10 -11 C
Positively Charged
C
4.67 x 1010 excess
electrons
-7.8 x 10 -12 C
Negatively Charged
Charge
Interaction
Mantra for Static Electricity
Opposites
attract;
and likes repel
Because of the away from nature of the mutual
interaction, the force is said to be repulsive.
Because of the towards each other nature of the mutual
interaction, the force is said to be attractive.
Additional Mantra for Static
Electricity
Any charged
object and
a neutral object
will attract each
other.
Electrical forces ____.
a. can cause objects to only attract each other
b. can cause objects to only repel each other
c. can cause objects to attract or repel each other
d. have no effect on objects
Positive or Neutral
Negative
Positive
Positive
Upon entering the room, you observe two balloons suspended
from the ceiling. You notice that instead of hanging straight
down vertically, the balloons seems to be repelling each other.
You can conclusively say ...
a. both balloons have a negative charge.
b. both balloons have a positive charge.
c. one balloon is charge positively and
the other negatively.
d. both balloons are charged with the
same type of charge.
Explain your answer.
Joshua is investigating the charge on several objects and makes the following
findings:
Object C
Object D
Object E
Object F
attracts B
repels C
attracts D
repels F
attracts A
Joshua knows that object A is negatively charged and object B is electrically
neutral. What can Joshua definitively conclude about the charge on objects
C, D, E, and F?
Explain your answer.
C
(-)
E
D
(+)
(-)
B
(0)
D
C
(-)
(-)
E
F
(+)
(+)
Object C
Object D
Object E
Object F
attracts B
repels C
attracts D attracts A
repels F
F
A
(+)
(-)
COULOMB’S LAW
K q1 q2
F=
2
r
K = 9.0 x
9
10
2
N·m
/
2
C
Coulomb’s Law Example #1
Suppose that two point charges, each
with a charge of +1.00 Coulomb are
separated by a distance of 1.00 meter.
Determine the magnitude of the
electrical force of repulsion between
them.
1.
Given: q1 = +1.00 C
q2 = +1.00 C
Unknown: F
r = 1.00 m
K = 9.0 x 10 9 N-m2/C2
Formula: F =
K q1q2
r2
Solution:
F = (9.0 x 10 9 N-m2/C2) (+1.00 C) (+1.00 C)
(1.00 m)2
F=
9.0 x 109 N-m2
1 m2
F=
9.0 x 10 9 N
Example #2
Two balloons are charged with an identical
quantity and type of charge: -6.25 C. They are
held apart at a separation distance of 61.7 cm.
Determine the magnitude of the electrical force
of repulsion between them.
2.
Given: q1 = -6.25 C
q2 = -6.25 C
Unknown: F
r = 61.7 cm -> ? m
K = 9.0 x 10 9 N-m2/C2
Formula: F =
K q1q2
r2
Solution:
F = (9.0 x 10 9 N-m2/C2) (-6.25 C) (-6.25 C)
(0.617 m)2
F=
3.5 x 1011 N-m2
0.38 m2
F=
9.2 x 10 11 N
Answer the following problems on your
notebook:
1. Two subatomic particles have an identical quantity and type of
charge: -2.35 C. They are held apart at a separation distance
of 2.5 m. Determine the magnitude of the electrical force
between the charges and what type of interaction is there
between the particles.
2. Two objects have different quantity and type of charge: the
first one is 2 C and the other is -2 C. They are held apart at a
separation distance of 20 m. Determine the magnitude of the
electrical force between the charges and what type of
interaction is there between the particles.
1.
Given:
q1 = -2.35 C
q2 = -2.35 C
Unknown: F
r = 2.5 m
K = 9.0 x 10 9 N-m2/C2
Formula: F = K q1q2 / r2
Solution:
F = (9.0 x 10 9 N-m2/C2) (-2.35 C) (-2.35 C)
(2.5 m)2
F=
4.97 x 1010 N-m2
6.25 m2
F=
7.9 x 10 9 N
Type of interaction: REPULSIVE