KEY ELEMENTS: PHYSICAL SCIENCE
Characteristics of Electricity (22‐25 hours)
Vocabulary
acetate, amperes, coulombs, current, electric force, electrons, energy, oules, kilowatt∙hours,
ohms, Ohm’s Law, power, resistance, series and parallel circuits, static charge,
Van de Graaff generator, voltage, volts
Knowledge
• static electrical charges
• relationships between charged objects
• electricity
• movement of charged particles
• electric current
• resistance and voltage
• Ohm’s Law
• series and parallel circuits
• power and energy consumption
1
Skills and Attitudes
• measure voltage and current using appropriate equipment
• perform calculations
• draw circuit diagrams
VOCABULARY
2
acetate, amperes, coulombs, current, electric force,
electrons, energy, joules, kilowatt hours, ohms, Ohm’s
Law, power, resistance, series and parallel circuits, static
charge, Van de Graaff generator, voltage, volts‰
KNOWLEDGE
• static electrical charges
• relationships between charged objects
• electricity
• movement of charged particles
• electric current
• resistance and voltage
• Ohm’s Law
• series and parallel circuits
3
• power and energy consumption
CONCEPTS
• explain, with illustrations, how static charges are
separated because of transfer between various
materials
• d
‰
escribe types of static electrical charge (positive,
negative) and no charge (neutral) with reference to
atomic theory
4
• d
‰
escribe how the electric force between two objects
depends on types of charge, size of charge, and the
distance between the two objects
CONCEPTS
• distinguish between
• potential and kinetic energy
• static electricity and electric current
• conventional current and electron flow
•‰
relate the charge on electrons to electron flow in a
circuit(i.e., from negative to positive)
5
•‰
define current in terms of the amount of electric
charge that passes a point in a given time interval
CONCEPTS
• define resistance
• draw circuit diagrams using appropriate symbols that are properly placed
• conduct experiments to
• measure voltage and current, using appropriate equipment and units (e.g., volts,
amperes)
• determine resistance, using current and voltage data
• perform calculations using Ohm’s Law
• for a fixed supply voltage, differentiate qualitatively between series and parallel
circuits in terms of
6
• current (may change for resistors in parallel; remains the same in series)
• voltage (may change for resistors in series; remains the same in parallel)
• total resistance (increases with the number of resistors in series; decreases in
parallel)
CONCEPTS
•‰
define electrical energy and power
•‰
calculate the following:
7
• power — using voltage and current data
• energy consumption — given the power rating of a device and duration
of use
8
7.1 STATIC ELECTRICITY
STATIC ELECTRICITY
9
What’s happening here?
STATIC ELECTRICITY
•
Sometimes called a Static Charge, static electricity
happens when electrons, collect on an object
•
Electrons are subatomic particles, they are one of the
particles that atoms are made of
•
Electrons, sometimes written as e− , have an electrical
charge of negative one, -1
•
Electrons come from the outer shells of atoms. Electrons
are not attached to the nucleus of the atoms, so they can
move easily from one atom to another in a material
10
What is Static Electricity?
11
STATIC ELECTRICITY
STATIC ELECTRICITY
• The type of atom that the electron is on, is important.
Some atoms are metals, and some atoms are non-metals
• Metals are atoms in which the electrons can move from
one atom to another easily
• Materials in which electrons move easily, are called
Conductors
• Non-metals are atoms in which the electrons can not
move from one atom to another, easily
12
• Materials in which electron can not move easily, are
called Insulators
•
Electrons are particles with a negative charge. Electrons
can only have a negative charge, -1
•
The other sub-atomic particles that atoms are made of are
Protons and Neutrons. Their charges are easy to remember
•
Protons are Positive, “Pro” reminds one of “Positive”, +1
•
Neutrons are Neutral, “Neu” reminds one of “None”, 0
•
Because Electrons can move from one atom to another,
those atoms can gain or lose a charge
•
They can become Ions (a noun) or Ionized (a verb)
13
STATIC ELECTRICITY
STATIC ELECTRICITY
What is Static Electricity?
• Static means “not moving”, so Static Electricity means
“electricity that is not moving”
• Static electricity happens when there is a large amount of
Charge on an object.
• If electrons are added to that object, the object will be
“Negatively Charged”
14
• If electrons have been removed from that object, the object
will be “Positively Charged”
STATIC ELECTRICITY
How can Static Electricity be made?
•
•
Friction occurs when objects rub against each other. The
friction between two objects can result in one object losing
electrons and the other object gaining electrons
Acetate is a type of plastic used in photographic film and
overhead transparencies. If the acetate strip is rubbed with
the paper towel, electrons will move from the paper towel
onto the acetate strip
The acetate strip will now have more negative charges than
positive charges. The paper towel, which lost the electrons,
will have more positive charges than negative charges
15
•
STATIC ELECTRICITY
16
How can Static Electricity be made?
STATIC ELECTRICITY
Conductor
17
Insulator
18
STATIC ELECTRICITY
19
STATIC ELECTRICITY
MEASURING CHARGE
• the unit of electrical charge is called the coulomb
(C)
• 1 C = 6250 quadrillion electrons!
6,250,000,000,000,000,000 electrons!
• a lightning bolt contains between 5-25 C of
negative charge
20
• a penny carries more than 1 million coulombs of
negative charge, but also more than 1 million
coulombs of positive charge
STATIC ELECTRICITY
•
People noticed or discovered Static Electricity before
Current Electricity
•
When the amount of Charge on an object got too great, it
would cause a spark. Lightning is a very big example of
this happening
•
It gave us ideas for charges, charged particles, and Ions
•
The ideas from Static Electricity are useful and important
for Current Electricity
21
Why is Static Electricity important?
22
7.2 ELECTRIC FORCE
ELECTRIC FORCE
Force is a push or pull, electric force can do both, without
touching the object. It is an action-at-a-distance force
•
Opposite charges
attract
•
Like charges repel
•
Neutral objects are
attracted to charged
objects
23
Laws of Static Charge
ELECTRIC FORCE
• Objects that have a charge may feel a force on
them
• Two objects with the opposite kind of charge will
attract each other (one is positive and one is
negative)
24
• Two objects with the same kind of charge will
repel each other (both are positive or both are
negative)
ELECTRIC FORCE
• Objects that have a charge may feel a force on
them
• Objects that have a neutral charge on them, have
equal amounts of positive and negative charges
25
• For objects with a neutral charge on the, imagine the
electrons moving on the surface, to the side away
from a negative charge object, or towards a
positive charge object
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ELECTRIC FORCES
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ELECTRIC FORCES
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ELECTRIC FORCES
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CHARGING BY CONDUCTION
1
2
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3
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CHARGING BY CONDUCTION
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CHARGING BY INDUCTION
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CHARGING BY INDUCTION