Transcript Electricity - pams

ELECTRICITY
Shoulder Partner
• Soon all cars, boats and airplanes will all
run on electricity.
• Do you agree or disagree with this
statement and why?
Electric Charge
• Protons and electrons both have the
property of charge. Remember, protons
are positive and electrons are negative.
• A force of attraction exists between
things that have opposite charges.
• A force of repulsion exists between
things that have same charges.
Electric Field
• An electric field
extends outward
through space from
every charged particle.
As things move close
to each other the
charge can jump to
another object.
Electricity Facts….
Table Talk
Was electricity invented or discovered?
What’s the difference between invention and
discovery?
Static Electricity
• Charge is only transferred
from one object to another.
This is called the Law of
Conservation of Charge.
• Static electricity – is the
buildup of electric charges on
an object.
Methods of Charging
• Friction – when two objects are rubbed together.
Ex: balloon on your hair.
• Conduction –direct contact of objects.
– Ex: plugging something in.
• Conductors – allow electricity to go
through easily
• Insulators – do not allow it to move
through.
• Induction – the jumping of electricity from one
object to another. Ex: a negatively charged
rubber rod can pick up tiny pieces of paper.
Electric Discharge
• Electric discharge – the loss of static
electricity. Sometimes slow and quiet, or
rapid with a spark of light, shock, or
crackle of noise.
• Ex: lightning.
Lightning Safety!
Circuits
• A circuit –forms when
a wire is connected to
the terminals of a
source forming a
complete path.
• Electric current – the
amount of charge that
passes a given point
per unit of time.
• The symbol for current
is I.
Face Partner
• How could you test to see if something
conducts electricity?
• How could you test to see which conduct
electricity better?
“Braniacs” on Electricity
Things to know…
• Georg Simon Ohm established the relationship
between electric current and potential difference.
• Resistance – ( R ) opposition to the flow of electric
charge
– ex: copper has low: iron has high
• Ohm -the unit to measure resistance.
• Ohm’s law – the current in a wire is equal to the
voltage divided by resistance or
• I = V/R
Superconductor
• Superconductor – a wire kept at extremely
low temperatures, resistance is zero.
High resistance…
If YOU were an electron…
Low resistance
Current direction
• DC (direct current) – electrons
that always flow in the same
direction. Ex: batteries
• AC (alternating current)
electrons that move back and
forth, reversing direction
regularly. (ex: current in home
changes direction every second
120x)
Table Talk
• What is the electrical difference between a
battery and an outlet?
• How are they also similar?
Circuits
• Electric circuit –
consists of a source of
energy; a load; wires,
and a switch.
• Sources: battery,
thermocouple,
photocell, or electric
generator
• Load – is what uses
the electricity
source
switch
wire
load
DRAW THIS!
SOURCES
•
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Battery – converts chemical to electrical
Photocell – converts light to electrical
Thermocouple – converts heat to electrical
Electric generator – converts mechanical
to electrical.
• Geothermal – earth’s
internal heat to electrical
Series vs Parallel
Series vs Parallel
• Series circuit – only one path to take; if
any part goes out the whole thing goes
out. Ex: old Christmas lights
• Parallel circuit – separate paths.
Ex: circuits in homes.
• Fuses – protect against too much current
flow
• Circuit breakers – similar to fuses but can
not burn out.
Series vs Parallel
Draw these…
Power
• Electric Power –the rate at which
electricity does work or provides energy.
- Measured in watts.
• Power = voltage x current
• Energy = power x time
Electric Safety
(Do not need to write)
•
•
•
•
•
Never handle when wet or near water
Never run wires under carpet
Never overload circuits
Repair worn out wires
Put nothing in electric sockets that does not
belong
• Never go by fallen wires or power lines
• In lightning storms get down to the ground by
crouching down low and stay away from trees.
• Safest spot in a lightning storm is inside a car.
Electric
Safety
Class Discussion
• What would happen if a
storm knocked out the
electricity in Virginia
Beach and it couldn’t be
restored for a month?
• What would the sequence
of events be?
Lastly!