Transcript Page 93 Static electricity is the buildup of electric charge on an

Page 91
S8P5.
Electricity
What is electricity and how is static electricity different from “regular”
electricity?
Most matter does not have an overall charge
(# of protons = # of electrons)
At times, matter can become charged either
positively or negatively. If an object has more
protons, it is positively charged. If an object
has more electrons, it is negatively charged.
These are called ions.
Objects can become charged by friction.
When objects made up of two different
materials rub against each other, the
electrons from one object can move to the
other object.
On page 90 – Write the question and answer
Imagine you are doing an experiment with static electricity.
You have a negatively charged balloon and a plastic comb.
You do not know whether the comb is positively or
negatively charged. What can you do to determine the
charge on the comb?
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Static electricity is the buildup of electric
charge on an object. Examples: balloon
rubbed against hair or clothes tumbling in a
dryer.
Static electricity can be discharged or released
slowly over time. Clothes with static
electricity will eventually lose their charge
over time because these charges will move to
the water molecules in the air. If you pull
apart clothes stuck together by static
electricity, static electricity is discharged
quickly (this is the crackling sound you hear)
Charged particles can exert forces on other
charged objects. The force between charged
particles is called electric force. Like charges
repel and opposite charges attract.
On page 92 – Write the questions and answers under each.
The protons in an atom are in the nucleus. The electrons of
the atom move around the nucleus. What keeps the
electrons from moving away from the nucleus?
If you charge a balloon by rubbing it on your hair and then
put the balloon against a wall, the balloon will stick to the
wall. The charge on the balloon induces a positive charge on
the wall and an electric force between the balloon and wall
causes the balloon to stick. If you leave the balloon alone, it
will eventually fall off the wall. Explain why.
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Electric charges do not always stay built up on
objects. Electric current is a flow of electric
charges through matter, and the rate that the
charges pass a given point. Electric currents can
transfer electrical energy to power devices such
as televisions and computers.
Electric current (I) is measured in the units
amperes or amps (A).
The amount of current flowing in a wire depends
on voltage and resistance. Voltage is a measure
of the potential energy per unit charge and is
measured in the unit of volts (V).
Resistance is the opposition to the flow of
electric charge and is measured in the unit of
ohms ()
Summary: EQ- What is electricity and how is static electricity different from “regular”
electricity?
Page 97
S8P5.
Electricity
What are the advantages and disadvantages of series and parallel
circuits?
Some materials have low resistance and
conduct electric current well. These are called
conductors and are often used to make wires.
Examples of conductors are copper, gold,
silver, tin, lead, etc.
Other materials have a resistance that is so
high that hardly any charges can flow through
them. Materials that do not conduct electric
current well are called poor conductors or
insulators. Examples of insulators are glass
and diamonds.
On page 96 – Create a 2 column table and categorize the following
materials as conductor or insulator.
Gold, silver, plastic, glass, wood, leather, tin, aluminum, lead, platinum,
ceramic, cloth, copper
Conductor
Insulator
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In solid conductors, the movement of electrons
carries the current. Current flows in wires and in
electric devices when the wires and devices are
connected in a complete closed path called a circuit.
All circuits contain three basic parts: an energy
source, a load and wires.
The energy source provides the voltage that causes
charges to flow as a current. Ex. battery
A load is a device in a circuit that changes electrical
energy into other kinds of energy. Ex. lightbulb
The wires of a circuit are used to connect energy
sources to loads.
Circuits may have several loads and many wires, but
often only have one energy source.
On page 98 – Create a 3 column table and categorize the following
materials as an energy source, load or wire (material for wire)
Battery, lightbulb, copper, gold, radio, electric generator, solar energy
cells, silver, tin
Energy Source
Load
Wire material
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There are two basic types of circuits: series and
parallel.
Loads connected together in a single loop are
called a series circuit. Because a series circuit is a
single loop, any break in the circuit will cause the
current to stop its flow.
Loads connected side by side are a parallel
circuit. In a parallel circuit, there are multiple
loops because each load is in its own loop.
Because each load is in its own loop, the circuit
will continue to allow the current to flow is one
of the loops is broken.
Summary: EQ- What are the advantages and disadvantages of series and parallel
circuits?
On page 100 – Draw a series and a parallel circuit each with 3 loads. Label
all the major parts and describe what will happen if one load fails in each
of the circuits.
Page 103
S8P5.
Magnetism
What are the differences between permanent magnets and
electromagnets?
A magnet is a material that exerts an attractive
force on certain other materials. Magnets are
made of elements such as iron, nickel or cobalt.
A magnetic force is a push or pull that is exerted
by a magnet. A magnet has two poles: a north
pole and a south pole. Each pole exerts a
magnetic force. If the poles are alike, the poles
repel (push away). If the poles are different,
they will attract (pull towards each other).
The area surrounding a magnet in which the
magnetic force exists is called the magnetic
field.
On page 102
Like poles repel or push away
S
N
N
S
Opposite poles create an attractive force.
S
N
The magnetic field of a bar magnet.
The field is represented by lines that
extend from one pole of the magnet
to the other. The lines are closest
together at the poles of the magnet.
This is the region where the
magnetic force is strongest. The
magnetic forces are weaker near the
center of the magnet where the lines
are farther apart.
S
N
N
S
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The production of a magnetic field by electric
current is called electromagnetism.
A magnet that is made by passing an electric
current through a coil of wire wrapped
around an iron core is called an
electromagnet.
Electromagnets are useful devices because
their magnetism can be turned on and off.
They are also useful because the strength of
the magnetic field can be controlled. This can
be accomplished in three ways: by changing
the amount of current flowing through the
wire, by adding or removing coils of wire, or
by changing the size of the iron core of the
electromagnet.
On page 104
Changing the Strength of an Electromagnet
To Increase Strength
To Decrease Strength
Increase strength of current
Decrease strength of current
Add more coils
Use fewer coils of wire
Increase size of iron core
Decrease size of iron core
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An electric motor is a device that transforms
electrical energy into mechanical energy.
Electromagnets are used in any device that
contains a generator. A generator is a device
that transforms mechanical energy into
electrical energy.
Summary: EQ- What are the differences between a permanent magnet and a
temporary magnet?
Page 109
S8P2.
Thermal Energy
What is the difference between thermal energy, heat and temperature?
Thermal energy is the total kinetic energy of all
particles in a substance. The thermal energy of
a substance depends on two factors: the
temperature of the substance and how much
substance there is.
Temperature is a measure of the average kinetic
energy of all the particles in a substance. When
the motion of a substance changes, the
temperature changes too. The faster the
particles move, the higher the temperature. The
slower the particles move, the lower the
temperature.
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Thermal energy and temperature are closely
related , but they are not the same.
Temperature is an average. It does not
depend on the amount of particles.
Heat is the flow of thermal energy. Heat
always moves from an area of higher
temperature to an area of lower temperature.
It will flow this way until all materials are the
same temperature.
Heat can be transferred in 3 ways:
conduction, convection and radiation.
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Conduction is the transfer of heat by direct
contact of particles. Ex. frying an egg
Convection is the transfer of heat in fluids
(including gases) by the movement of
currents. Ex. boiling rice
Radiation is the transfer of heat without
matter. Ex. sun shining
Conduction and convection require matter,
radiation does not require matter.
Summary: EQ- What is the difference between thermal energy, heat and
temperature?