UNIT D: ELECTRICAL PRINCIPLES

Topic 1: Transfer and Storage of Electrical Energy

I. REVIEWWhat is electricity?

•Is the energy of charged particles

•Is when electrons are moved

Remember: Electrons are the outer particle of an atom

I. REVIEWAll matter is made of particles; Particles

are atomsAtoms are made of 3 sub-atomic

particles:1. Neutrons – neutral (0) particles2. Protons – positive (+) particles3. Electrons – negative (-) particles

I. REVIEW Draw an atom!

I. REVIEW Atoms are neutral – this means :

# of protons = # of electrons Being charged means having unequal

protons and neutrons +++ - - - -+ - +- -- - - - -++

Easiest method of charging, is through friction!!!

II. STATIC ELECTRICITYA. Laws of Electrical ChargeOpposite charges attract (+ and – will attract) Like charges repel (ex. + and + will repel)

ACTIVITY: CHARGE ITTo witness the action of uncharged/

charged objects on each other.

Remove charges from objects by running through your hand

Charge objects by running through paper towel or fur

ACTIVITY : CHARGE ITTrial Strip Balanced on

Watch GlassHand-Held Strip

Behavior of Balanced Strip

1 Uncharged acetate Uncharged acetate

2 Uncharged acetate charged acetate

3 charged acetate charged acetate

4 charged acetate Uncharged vinyl

5 charged acetate Charged vinyl

6 Charged vinyl Charged vinyl

7 Uncharged vinyl Uncharged vinyl

I. STATIC ELECTRICITYDefinition: The state of having unequal

number of protons and electrons ; is an UNMOVING charge

“static” means not moving; charge DOES NOT flow constantly (vs. current electricity where charges

are flowing)

I. STATIC ELECTRICITY A. Charge Separation Occurs when a charged object is

brought close to a neutral objectThe same charges will repel, causing

the opposite charges to attract

EX. WHY A BALLOON (-) RUBBED ON YOUR HEAD STICKS TO THE WALL - DRAW!

B. ELECTRICAL DISCHARGE Although static electricity does not move,

it is “discharged” Is the process of built up electrons

transferring to other objects (Shocked!)Ex. lightning

Electric eel

Simulation

Electric eels work to kill or stun prey by using electrical discharge of static electricity

B. ELECTRICAL DISCHARGEDischarging makes the charges

between objects equal [Draw objects : Before / After ]

B. ELECTRICAL DISCHARGEGrounding – a method of discharging

an object Done by connecting object with a wire

to the Earth (it can absorb lots of electrons)

C. VAN DER GRAFF GENERATORSo Used to study electrical dischargeso Electrons build up on the outside sphere

through friction -> the electrons seek to be discharged

WHAT IS THE DIFFERENCE BETWEEN CURRENT

ELECTRICITY AND STATIC ELECTRICITY?

Current electricity is a flow of electrons

Static electricity is a build-up of charges (+ or -)

A. CIRCUIT Is a path of electron flow

Usually includes: source (battery) conductor (wire) load (lamp or device) switch (opens or closes a circuit)

• Must be complete /closed for electricity to flow

SIDENOTE:Microcircuits –small circuits with low

voltage and current.

Where have you seen these

parts before?

Circuit symbols:

resistor

lampwire

switch

Cell (battery)

- +

A. CIRCUITS Schematic diagrams – a neat

representation of a circuit using circuit symbols

B. TERMS OF CURRENT ELECTRICITYConductors – materials which allow the

flow of electrons (ex. Metals, water)Insulators – materials which prevent

(resist) the flow of electrons (ex. Plastic)Load – a device which converts

electrical energy to other forms of energyEx. Lamp, Radio, Motor

B. TERMS OF CURRENT ELECTRICITY

Current Voltage Resistance

What is it?

Rate at which electrons are flowing

How much energy each electron carries

How difficult it is for electrons to move

How is it measured?

Using an ammeter connected in parallel

Using a voltmeter in series

Using an ohmeter or galvaonmeter

What is the unit?

Unit is Amperes (A)

Unit is Volts (V) Unit is Ohm’s

B. TERMS OF CURRENT ELECTRICITY Examples:

1. What is the difference between 1.0A and 3.0A?

2. What is the difference between 1.5V and 9.0V?

3. What is the difference between 2.0 and 6.0 ?

VIDEO

How could the following picture be a metaphor for: currentvoltage resistance

B. MODELING ELECTRICITY

Ex. Waterfalls

Current – how quickly the water is flowing down the waterfall

Resistance – how many rocks are in the stream bed, preventing the flow of water

Voltage – the height of the waterfall (how much energy the water has)

C. CELLS AND BATTERIESCells and batteries create

current electricity in a circuit >Create the electron flow

C. CELLS AND BATTERIESI. Basic TermsElectrochemical Cell – a

device that transforms chemical energy into electrical energyEx. AA, AAA – all 1.5V

“batteries” are actually cells

I. BASIC TERMSBatteries –multiple cells joined

together to create a larger voltage

ACTIVITY: CELL VS. BATTERY Predict the voltage of each of the following:

# of Cells Connected Voltage reading (V)

1

2

3

4

5

Remember: 1 cell = 1.5V

I. BASIC TERMSDry cells – when the electrolyte is a

pasteWet cells- when the electrolyte is a

solution

I. BASIC TERMSPrimary cells – cells that cannot be recharged Ex. Manganese-oxide alkaline batteriesSecondary cells – cells that can be recharged

by using electrical energy to reverse the chemical reaction“rechargables”

Ex. Car batteries, cell phones, Ni-Cd batteries - will wear out over time

II. PARTS OF AN ELECTROCHEMICAL CELLo 1 or 2 Electrolytes – a solution or paste that

conducts electrolytes (ions)o 2 Electrodes – metals/ solids conductors

(allow movement of e-)o Made of different metals o Cathode is positive (receives electrons) o Anode is negative (gives away “Source” of

electrons)

III. How A Cell Works1. Electrons are transferred from the

negative electrode through a wire – head to the load

(-)(+)

III. HOW A CELL WORKS2. Ions (Ex. Cu2+(aq)) from the electrode

are transferred through the solution (electrolyte) to the positive electrode.

3. The anode eventually is “eaten away” or used up (-)(+)

DRAW A CELL IN ACTION!DRAW A CELL WITH THE FOLLOWING PARTS: -COPPER ELECTRODE, COPPER SOLUTION -NICKEL ELECTRODE, NICKEL SOLUTION -WIRE -BULB -2 BEAKERS

CELL LAB: EVALUATING CELL DESIGN Summarize the following:

1) What affect does decreasing the concentration of an electrolyte have on the voltage of a cell?

2) What affect does using the same electrodes have on the voltage of a cell?

3) What affect does using different combinations of electrolytes have on the voltage of a cell?

IV. APPLICATIONS OF CELLS AND BATTERIES

o We can apply batteries in useful ways:

Electrochemistry – the study of chemical reactions to produce electricity

1) Electrolysis – using a battery (electricity) to split a compound into its elements

Ex. H20 -->

IV. APPLICATIONS OF CELLS AND BATTERIES

2) Electroplating – coating a metal with a thin layer of a wanted metal

The object to be plated is connected to the (-) negative electrode of the batteryEx. Plating inexpensive jewelry with gold

IV. APPLICATIONS OF CELLS AND BATTERIES3) Galvanizing–coating parts with a layer

of aluminum oxide (is much harder than aluminum) Ex. Jewellery, screen doors, kitchenware

IV. APPLICATIONS OF CELLS AND BATTERIES

4) Electrorefining –removing impurities from metals

-impure metals are placed at (+) electrode and a pure metal is placed at (-) terminal.

CONNECT A CIRCUIT SO THAT TWO LIGHT BULBS CAN BE SWITCHED ON AND OFF TOGETHER.