Transcript ELECTRICITY

ELECTRICITY
Explain
Atomic Structure Review
p+ - nucleus
 no - nucleus
 e- - electron cloud
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atoms have a neutral
charge
 net charge of “0”
 atoms become charged
by gaining or losing
electrons
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IONS – charged atoms
 + or 
Electroscope – instrument used to detect
electric charge.
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Atoms can gain or lose electrons based on
their environmental conditions.
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Static Electricity – excess electric (having
extra electrons) in an object
◦ Feet on carpet
◦ Balloon on hair
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Electrically charged objects follow a set of rules:
1. Law of Conservation of Energy (Charge)Charges may be transferred but not created or
destroyed.
2. Opposite charges attract. Like charges repel.
Think MAGNETS.
3. Charges act at distances. (Because of electric field).
Objects closer together (shorter distance) will have a
greater attraction.
Objects farther apart (greater distance) will have a
lesser attraction.
4. Electrons move more easily through conductors.
5. Electrons are inhibited by insulators.
Transferring Electric Charge
Happens by
Contact – touching, rubbing
Induction – closeness to
something of opposite
charge. (balloon close to
shirt)
Static Discharge – transfer through
air (electrons built up in air)
EX: lightning
Grounding – using a conductor to direct an
electric charge to the ground.
EX: lightning rods
Electric Current
-flow of electrical charges through a
conductor
-electrical charges are…….ELECTRONS
-conductor is made of……….METAL
-current is measured in amperes (A)
Remember: Electrons are IN EVERYTHING!!
They simply need a path and a push to
move.
Charges (e-) flow from high voltage to low
voltage
-Voltage DIFFERENCE is what causes
charges to “flow” (push)
-Voltage (the push) is measured in
Volts (V)
-Current flow must happen in a
CIRCUIT - a closed path on which
electrons travel
Resistance – tendency for a material to
“oppose” the flow of electrons.
-will change electrical energy into
thermal energy and/or light.
-all materials have some electrical
resistance
-measured in Ohms ( Ω )
-making wires thinner, longer or hotter
increases the resistance.
Ohm’s Law:
the current in a circuit =
the voltage difference / the resistance.
I = V/R
I (current) labeled in Amperes
Electrical Circuits:
 circuits rely on generators at power plants
to create a voltage difference at an outlet
(plug-in)
 wall socket – voltage difference across the
two holes of an electrical outlet.
 when the circuit is “complete” or
“something is plugged in,” the charge can
move from high to low.
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Series Circuit
one loop
current is the same
at any part of the
circuit
Interrupting
(opening) the circuit
will cause the whole
thing to turn off
EX: x-mas lights (old)
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Parallel Circuit
multiple loops
current can flow to
individual parts of the
circuit
interrupting
(opening) the circuit
will not affect the
whole unit
electrical system in a
house
x-mas lights (new!)
Household Electricity:
-standard voltage difference generated
by outlets
~120V – regular outlet
-tv, microwave, phone
charger, clock, vacuum
~240V – high power outlet
-washer, dryer, oven,
camper/rv
Electricity enters your home at…….. a fuse
box or a circuit breaker, then branches out
to your sockets and lights.
 Objective of the fuse box or circuit
breaker: guards against electric
overheating.
 Electrical energy is easily converted into
mechanical, thermal, or light.
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Electrical Power:
(remember power is a rate)
~rate at which electrical energy is
converted into another form of energy.
 labeled W – Watts or kW – kilowatts
P = IV
 Calculating energy:
kWh – kilowatt hour
E = Pt
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