ELECTRICITY
Notes vs Discussion
• In this chapter we will write out our class
notes
– Your are to write any information that is in
RED
– Anything in black does not need to be copied
by you.
– Your outline will only consist of practice
worksheets and lab activities for this chapter.
Atom
• .
Nucleus
Electron
ATOMIC
BOMB
NUCLEAR
POWER
Electricity
The ATOM
Electrons
(Negatively charged)
The atom is made of 3
basic parts:
1. Protons
2. Neutrons
3. Electrons
Nucleus
Neutrons
(Neutral)
Protons
(Positively
charged)
HYDROGEN
(Proton)
Nucleus
Protons
Neutrons
NUCLEUS + ELECTRONS = ATOM
# PROTONS
=
# ELECTRONS
# PROTONS
>
# ELECTRONS
Missing Electron
# PROTONS
<
# ELECTRONS
Extra Electron
Electric charge
• 2 Types
• Pos charge - more protons than electrons
• Neg charge - more electrons than protons
• Neutral - same amount of protons and
electrons
Atoms become “charged” when
they gain or lose electrons
• Gain electrons = become - charged
• Lose electrons = become + charged
• Protons do not move from atom to
atom.
• The natural state of any atom is to be
neutral.
– If an atom becomes “charged” we call it an
Ion.
Law of Electrical Charges
Different charges attract
Same charges repel
Demo
Another way to show
attract and repel
The act of repelling or attracting occurs
because of Electric Forces
Electroscope – A device used to
detect a static electrical charge.
Static Electricity - The build up, or collection of negative
charges on an object causing an electric field around that
object.
Why does
your hair
do this??
Each hair
becomes
negatively
charge and
therefore
REPELS
each other.
Electric Discharge
-The rapid movement of excess
charge from one place to another.
– Sparks (Small discharge)
– Lightning bolts
(Large discharge, millions of volts)
Lightning
- a large electrical discharge between
the atmosphere and ground.
• 3 ways lightning can strike
– Cloud to ground
– Ground to cloud
– Cloud to cloud
Formation of Lightning
1. Collection of negative charges in cloud.
2. Ground becomes positive.
3. Stepped leader forms in between and
makes connection with ground
4. Invisible discharge takes place
5. Return stroke that we see.
1. 4 – 6 return strokes can take place during one
strike.
+++++++++++++++++++++++++++++++
Positively charged at the top
___ ___Negatively charged towards bottom ___ ___ ___
___ ___ ___ ___ __ __ __ __ __ __ __
The lightning we
see “return stroke”
Stepped Leader
forms first
++++++++++++++++Positively charged ground++++++++++++++++++++++
Invisible
Channel is very
jagged and
unpredictable.
Types of Lightning
• Ribbon lightning
Ball Lightning
Sheet Lightning
Bead Lightning
Red Sprites
Blue jets
Lightning and Thunder
1mile every 5 seconds
Electric Circuits
Circuit – A closed conducting pathway
for electrons to flow through.
The “flow of electrons” is called
Electric current
Electric current
is a lot like the
flow of water
through pipes
Simulation
Simple Circuits
• 3 parts to a simple Circuit
–1. Source of Electricity
»“battery”
–2. Conductor
»“wire”
–3. Load
»“Light bulb or motor”
»What electrons do work on
Simple Circuit
Source
+
_
Conductor
Load
Simple Circuit
Source
+
_
Conductor
Load
Batteries and Bulbs
“Student Challenge!!!!!!”
Can you and your partner work together to make the
light bulb light up!!!! Use only the battery, bulb (with no
socket, and a piece of wire. There are ten different
combinations. Try to figure out all ten. You must make
a drawing of how you arrange the items to make the
bulb light using the symbols below. Good Luck!!!
Clue # 1
Touch here
Touch here
Clue #2
Clue #3
Conductors (very low resistance)
Materials allow electrons to flow easily.
Used in electrical circuits.
silver
copper
gold
aluminum
iron
steel
brass
bronze
mercury
Insulators (very high resistance)
Don't allow electrons to flow easily.
Used to protect ourselves.
glass
rubber
asphalt
fiberglass
cotton
paper
wood
plastic
air
Resistors (known as a semi-conductor)
Allow a small amount of electrons to pass
through. Much less than a conductor. Becomes
hot due to friction. This heat is USEFUL!
Graphite
Carbon
Tungsten
Silicon
Nickel
The Incandescent light bulb
Argon gas
Tungsten Filament is double coiled to
allow for up to 2 feet of wire give off the
glow.
Source of Electricity (Battery)
•Supplies electrical potential energy to a circuit.
•Sets the voltage of the circuit.
2 types of batteries
Dry Cell
Wet Cell
Wet Cell versus Dry Cell
•Used in automobiles
•Used in small electronic
equip.
•High voltage (12v)
•Low voltage ( 1.5v)
•Short life
•Long life
•Needs recharged often
•Carbon center +
•Liquid electrolyte (salt
or acid)
•Zinc outer case -
•Lead plates
•Manganese paste
electrolyte
Electrical Symbols
•Source
•Voltmeter
•Light bulb
•Ammeter
•Motor
•Resistance
•Switch on
•Fuse
•Switch off
Series Circuits – a circuit that has
only a single path (one loop) for
current to flow through all of its
parts.
Bulbs in Series
Batteries in Series
Parallel Circuits - requires more
than one path for current flow in
order to reach all of the circuit
parts.
Batteries in Parallel
Ohm’s Law
• The relationship between the voltage,
amperage, and resistance in an electric
circuit.
Voltage
Voltage= The amount of electrical
potential energy given
to circuit.
“The pressure or push on
electrons”
Measured in Volts
Symbol = V
Voltage = Amperage x Resistance
Formula
V=IxR
220 volts = 11 amps x 20 ohms
Resistance
Resistance= How difficult it is for
electrons to travel
through a material
“The friction from electrons,
produces light and heat”
Measured in ohms
Symbol =
Resistance = Voltage / Amperage
Formula
R=V/I
30 ohms = 90 volts / 3 amps
Amperage
Amperage=
The amount of current
that passes a given
point in one second.
“The flow of electrons”
Measured in Amps
Symbol = I
Amperage = Voltage / Resistance
Formula
I=V/R
6 amps = 12 volts / 2 ohms
Alternating Current
• Electric current that travels back and forth
in a circuit.
– Changes direction 60 times in a second!!!
– Much more intense than Direct Current
– Created by a generator (magnets inside)
– Can travel great distances
Direct Current
• Electric current that travels only in one
direction.
– Produced by chemical reactions (batteries)
– Low intensity
Voltage
Amperage
Resistance
Fuses and Circuit Breakers
Devices that open a circuit due to overload.
(drawing too much current)
* prevents
damage or potential fire
Fuses – open a circuit when a
narrow filament melts. Not
reusable.
New Fuse
Blown Fuse
Breakers – a switch that automatically opens
a circuit when overload occurs. Reusable
Switch can be opened 3 different ways.
1. heat from circuit causes
bimetallic strip to separate 2 metals.
2. electromagnet breaks circuit
3. small explosion
Calculating Electrical Cost
Step 1 – Calculate wattage (volts X amps)
220 volts X 3 amps = 660 watts
Step 2 – Convert watts to Kilowatts (X .001)
or divide by 1000
660 X .001 = .66 kilowatts
Step 3 – Multiply kilowatts by the amount of
time used. All numbers must be in hours.
.66 kilowatts X 3 hours = 1.98 Kilowatt - hours
Step 4 – Multiply Kilowatt – hours by the
rate or price (around $0.10)
1.98 X .10 = $0.19
Power
- the rate at which a device
converts electricity into another
form of energy.
Answer labeled as Watts
•
•
•
•
Electric oven - electricity into heat
Motors - electricity into motion
Toaster – electricity into heat
Hair dryer – electricity into heat and
motion