Unit D: Electrical Principles
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Transcript of Unit D: Electrical Principles
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UNIT D: ELECTRICAL PRINCIPLES
Topic 1: Transfer and Storage of Electrical Energy
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I. REVIEWWhat is electricity?
•Is the energy of charged particles
•Is when electrons are moved
Remember: Electrons are the outer particle of an atom
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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
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I. REVIEW Draw an atom!
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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!!!
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II. STATIC ELECTRICITYA. Laws of Electrical ChargeOpposite charges attract (+ and – will attract) Like charges repel (ex. + and + will repel)
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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
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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
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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)
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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
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EX. WHY A BALLOON (-) RUBBED ON YOUR HEAD STICKS TO THE WALL - DRAW!
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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
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Electric eels work to kill or stun prey by using electrical discharge of static electricity
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B. ELECTRICAL DISCHARGEDischarging makes the charges
between objects equal [Draw objects : Before / After ]
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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)
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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
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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 -)
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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
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SIDENOTE:Microcircuits –small circuits with low
voltage and current.
Where have you seen these
parts before?
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Circuit symbols:
resistor
lampwire
switch
Cell (battery)
- +
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A. CIRCUITS Schematic diagrams – a neat
representation of a circuit using circuit symbols
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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
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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
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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 ?
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VIDEO
How could the following picture be a metaphor for: currentvoltage resistance
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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)
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C. CELLS AND BATTERIESCells and batteries create
current electricity in a circuit >Create the electron flow
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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
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I. BASIC TERMSBatteries –multiple cells joined
together to create a larger voltage
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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
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I. BASIC TERMSDry cells – when the electrolyte is a
pasteWet cells- when the electrolyte is a
solution
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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
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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)
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III. How A Cell Works1. Electrons are transferred from the
negative electrode through a wire – head to the load
(-)(+)
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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 (-)(+)
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DRAW A CELL IN ACTION!DRAW A CELL WITH THE FOLLOWING PARTS: -COPPER ELECTRODE, COPPER SOLUTION -NICKEL ELECTRODE, NICKEL SOLUTION -WIRE -BULB -2 BEAKERS
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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?
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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 -->
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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
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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
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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.
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CONNECT A CIRCUIT SO THAT TWO LIGHT BULBS CAN BE SWITCHED ON AND OFF TOGETHER.