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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 ATOMIC BOMB
Nucleus NUCLEAR POWER
Electron Electricity
• .
The ATOMThe atom is made of 3 basic parts:
1. Protons
2. Neutrons
3. Electrons
Protons
Electrons
Neutrons
Nucleus
(Negatively charged)
(Positively charged)
(Neutral)
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.
Same charges repel
Different charges attract
Law of Electrical Charges
Demo
Another way to show attract and repel
The act of repelling or attracting occurs because of Electric Forces
Why does your hair do this??
Each hair becomes negatively charge and therefore REPELS each other.
Static Electricity - The build up, or collection of negative charges on an object causing an electric field around that object.
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.
___ ___Negatively charged towards bottom ___ ___ ___ ___ ___ ___ ___ __ __ __ __ __ __ __
+++++++++++++++++++++++++++++++
Positively charged at the top
Stepped Leader forms first
++++++++++++++++Positively charged ground++++++++++++++++++++++
The lightning we see “return stroke”
Electric Circuits Circuit – A closed conducting pathway
for electrons to flow through.
The “flow of electrons” is called
Electric currentElectric 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
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!!!
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!
GraphiteCarbon
TungstenSiliconNickel
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 batteriesDry Cell Wet Cell
Wet Cell versus Dry Cell
•Used in automobiles
•High voltage (12v)
•Short life
•Needs recharged often
•Liquid electrolyte (salt or acid)
•Lead plates
•Used in small electronic equip.
•Low voltage ( 1.5v)
•Long life
•Carbon center +
•Zinc outer case -
•Manganese paste electrolyte
Electrical Symbols•Source
•Light bulb
•Motor
•Switch on
•Switch off
•Voltmeter
•Ammeter
•Resistance
•Fuse
Series Circuits – a circuit that has only a single path (one loop) for current to flow through all of its
parts.
Bulbs in Series
Parallel Circuits - requires more than one path for current flow in order to reach all of the circuit
parts.
Ohm’s Law
• The relationship between the voltage, amperage, and resistance in an electric circuit.
Voltage
“The pressure or push on electrons”Measured in
Voltage=
Formula
Voltage = Amperage x Resistance
V = I x R
Symbol = V
The amount of electrical potential energy given to circuit.
220 volts = 11 amps x 20 ohms
Volts
Resistance
“The friction from electrons, produces light and heat”
Measured in
Resistance=
Formula
Resistance = Voltage / Amperage
R = V / I
Symbol =
How difficult it is for electrons to travel through a material
30 ohms = 90 volts / 3 amps
ohms
Amperage
“The flow of electrons”
Measured in Amps
Amperage=
Formula
Amperage = Voltage / Resistance
I = V / R
Symbol = I
The amount of current that passes a given point in one second.
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
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.
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 CostStep 1 – Calculate wattage (volts X amps)
Step 2 – Convert watts to Kilowatts (X .001) or divide by 1000
Step 3 – Multiply kilowatts by the amount of time used. All numbers must be in hours.
Step 4 – Multiply Kilowatt – hours by the rate or price (around $0.10)
220 volts X 3 amps = 660 watts
660 X .001 = .66 kilowatts
.66 kilowatts X 3 hours = 1.98 Kilowatt - hours
1.98 X .10 = $0.19