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)

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.

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

Electroscope – A device used to detect a static electrical charge.

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”

Invisible Channel is very jagged and unpredictable.

Types of Lightning

• Ribbon lightning

Ball Lightning

Sheet Lightning

Bead Lightning

Red Sprites

Blue jets

Lightning and Thunder1mile every 5 seconds

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

Simple Circuit

+_

Conductor

Source

Load

Simple Circuit

+_

Conductor

Source

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!

GraphiteCarbon

TungstenSiliconNickel

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 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

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

“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

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 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

Power

• Electric oven - electricity into heat

• Motors - electricity into motion

• Toaster – electricity into heat

• Hair dryer – electricity into heat and motion

- the rate at which a device converts electricity into another form of energy.

Answer labeled as Watts