Transcript closed circuit - Cobb Learning

Negative
charges in an
atom are called
___________.
electrons
Rules
1. Like charges repel
one another
2.Unlike charges
attract one another
3
What kind of
electricity can be
caused by rubbing
two materials
together?
When you rub a balloon
with a cloth, __________
negative
charges are knocked
off the cloth and are
collected onto the
balloon. This makes
the balloon have a
negative charge.
__________
The van de Graaf generator (large silver
ball) deposits electrons on the ball.
When a person places their hand on the
ball and the machine is turned on,
electrons are transferred to and
collected on the person touching the
silver ball.
Why do you
think this
machine
affects the
hair of the
children in
the picture?
What is a discharge
of static electricity
in the atmosphere
called?
Lightning occurs when
negative charges
the ___________
in the thundercloud
build up and jump to
positively charged
the ____________
ground.
What is an electric
shock?
• When the electric current
enters your body.
• The amount of current depends on
whether it is fatal or not.
What are some things you
should know about lightning
safety?
• Take shelter inside if you hear
thunder or see lightning.
• Avoid open fields and high places of
elevation.
• Avoid isolated objects (trees in a
field)
• Avoid metal objects (bleachers,
picnic shelters) and bodies of water
• If you cannot go inside then
assume the “duck-cover position”
What are the rules about
electrical forces?
• The positively charged protons in
the nucleus attract the negatively
charges electrons in the energy
levels and hold them in place.
• The closer the objects are that
are attracted to each other the
stronger the electrical forces.
• Like charges repel and unlike
charges attract.
What is an electric
field?
• Electric forces exerted at a
distance between two objects
create the electric field.
What is grounding?
• Grounding is the use of a
conductor to send a large
electric discharge into a
substance that cannot be
harmed instead of following the
path that it would normally
follow.
• Example: sending lightning into
the Earth instead of into a
house
What kind of
electricity is caused
by a continuous
flow of electrons?
Current
• Flow of electrons
through a conductor
• Measured in amperes
(A)
15
Voltage
• A difference in
electrical potential
• Measured in volts
16
What is the path
that electricity
flows through
called?
A circuit must be
closed to allow
_________
the flow of
electricity.
Electrons flow thru a circuit
because of the applied voltage
across the circuit (Ohm’s Law)
What is the difference between an open
circuit and a closed circuit?
A closed circuit is one in which the pathway
of the electrical current is complete
and unbroken.
An open circuit is one in which the pathway
of the electrical current is broken. A
switch is a device in the circuit in
which the circuit can be closed (turned
on) or open (turned off).
How many
pathways does a
series circuit
have?
Series Circuit
• Current flows through
a single path.
21
Series Circuit
•If the path is broken at
any point, current flow
stops.
•Ex: Old Christmas
lights
22
How many
pathways does a
parallel circuit
have?
Parallel Circuit
• Current flows through
multiple paths.
24
Parallel Circuit
•If one path is broken,
current continues to
flow through other
paths.
•Ex: House wiring
What can be
used to control
the flow of
electricity?
What do we call
materials that
allow the flow of
electricity?
What do we call
materials that do
not allow the flow
of electricity?
What is a conductor and insulator?
A conductor is a material which
allows an electric current to pass.
Metals are good conductors of
electricity.
An insulator is a material which
does not allow an electric current
to pass. Nonmetals are good
conductors of electricity.
Plastic, glass, wood, and rubber
are good insulators
What is a poor
conductor called?
Resistors allow
electrical energy
to be ___________
changed
into other forms
of energy.
Resistance
• The opposition to the
flow of electrons
through a conductor
• Measured in ohms ())
Ohm’s Law
• Relationship between
voltage, current, &
resistance
• Current = voltage
resistance
or I = V / R
Direct Current (DC)
• Electrical current
that flows in only
ONE direction
• Ex: Batteries
Alternating Current (AC)
• Electrical current that
changes direction as it
flows
• Ex: Homes wired to an
electrical power grid
In DC, the electrons flow
steadily in a single
direction, or "forward."
In AC, electrons keep
switching directions,
sometimes going
"forwards" and then going
"backwards."
Name three types
of energy that
electricity can be
changed into.
Heat, light, and
mechanical energy
Electrical Power and Cost
• Electrical power is
measured in watts (W)
• Electricity is calculated in
KiloWatt-Hours
How is the cost of your
electricity determined?
• Power is the rate at which
energy is used, or the amount
used per second.
• Electricity is sold in kilowatt
hours (1,000 watts).
• 1kW is the amount of electrical
energy for 1 hour.
• 10 100-W light bulbs for 1 hour or
one 100-W bulb for 10 hours.
What is the
area of
magnetic
force
called?
Electric current
creates a
magnetic field.
_____________
Magnetism
• Like poles attract
• Unlike poles repel
• Magnetic fields are
strongest near the
poles.
Magnetic Fields
• Field flows
North to
South
What do you make if
you put together a
closed circuit and wrap
the wire around an iron
bolt?
Electromagnet
How can you make
an electromagnet
stronger?
You can wrap the
wire around the iron
bolt more times.