concept 2
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Concept 2. Energy Transfer. Concept 2 Vocabulary Terms. Static electricity Proton Electron Neutral Charge separation Electrical discharge Electrical current Circuit Amperes (A). Conductors Load Voltage Potential difference Volt (V) Voltmeter Short circuit Insulators Fuses - PowerPoint PPT PresentationTRANSCRIPT
Concept 2Energy Transfer
CONCEPT 2 VOCABULARY TERMS
Static electricity Proton Electron Neutral Charge separation Electrical discharge Electrical current Circuit Amperes (A)
Conductors Load Voltage Potential difference Volt (V) Voltmeter Short circuit Insulators Fuses Circuit breakers
CONCEPT 2 VOCABULARY TERMS
Electrochemical cell Dry cell Electrolyte Ion Electrode Wet cell Primary cell Rechargeable cell Secondary cell Battery
Electrolysis Electrochemistry Electroplating
CONCEPT 2 – VOCABULARY TERMS
Conductor Insulator Resistor Resistance Ohms (Ω) Variable resistor Rheostat Ohm’s Law Ammeter Schematic
Schematic diagram Series circuit Parallel circuit Transistor Microcircuit
CONCEPT 2 – ENERGY TRANSFERLearning Concept
Investigate and evaluate the use of different electrodes, electrolytes and electrolytic concentrations in designing electrical storage cells
CONCEPT 2 – ENERGY TRANSFER Recall:
Chemical energy is transformed into electrical energy in battery-powered devices
An electrochemical cell is a device which has different metals in a solution containing a salt or acid
CONCEPT 2 – ENERGY TRANSFER In an electrochemical cell, there are two
metal electrodes surrounded by an electrolyte, a substance that can conduct electricity
CONCEPT 2 – ENERGY TRANSFERLearning Concept
Assess the potential danger of electrical devices, by referring to the voltage and current rating (amperage) of the devices
Distinguish between safe and unsafe activities
CONCEPT 2 – ENERGY TRANSFER
Two aspects of electricity must be considered when looking electrical dangers Voltage
The measure of how much energy is carried by each particle
Ampere The rate at which an
electrical current flows
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CONCEPT 2 – ENERGY TRANSFER
High voltage is more dangerous than low voltage
Small voltages can kill if the shock carries a significant amount of amps The number of amps
is more important than voltage when assessing potential danger
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CONCEPT 2 – ENERGY TRANSFER 50,000 V is more likely to kill than 10 V 0.001 A passed through your body won’t
likely be felt Current in the range of 0.015 A to 0.02 A
causes a painful shock and loss of muscle control Currents as low as 0.1 A can be fatal
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Electric eel can discharge 600 V at 1.0 A
CONCEPT 2 – ENERGY TRANSFER Taser (stun) guns
can carry up to 50,000 volts Can deliver up to
1,500 V to a person’s body
Small current of 0.002 to 0.03 amps
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CONCEPT 2 – ENERGY TRANSFER Electrical outlets
in Canada deliver 120 volts of electricity
A light bulb draws about 0.5A while a toaster pulls 5A
Possible to suffer fatal shock from a household outlet
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CONCEPT 2 – ENERGY TRANSFERScience Log Make a list of 5 safety pointers for use with
electrical devices (reference pg 285) ex. Do not use electrical devices when near or in
water unless they are specially designed
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CONCEPT 2 – ENERGY TRANSFER Learning Concept
Distinguish between static and current electricity Identify example evidence of each
CONCEPT 2 – ENERGY TRANSFER Recall:
The proton has a positive charge The electron has a negative charge
Most objects have equal amounts of positive and negative charges, which makes them neutral
CONCEPT 2 – ENERGY TRANSFER Charge separation occurs when charged
objects are brought close to neutral objects
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CONCEPT 2 – ENERGY TRANSFER
Rubbing the balloon on your hair transfers electrons (e-) from your hair to the balloon
Bringing the charged balloon to the wall repels the e- in the wall but attracts the protons
CONCEPT 2 – ENERGY TRANSFER The Laws of Electrical Charges
Opposite charges attract each other Like charges repel each other
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CONCEPT 2 – ELECTRICAL ENERGY Electrical discharge is observed as a
spark Static energy does not flow in a current but can
build up and discharge Electrons build up in your body Doorknob becomes positively charged as “your”
electrons repel the doorknob electrons “Your” electrons are attracted to the doorknob’s
protons
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CONCEPT 2 – ENERGY TRANSFER Van de Graaff generator
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CONCEPT 2 – ENERGY TRANSFER While static energy builds up and
discharges, it does not flow continuously Electrical currents are steady flows of
charged particles This is the type of energy used to operate
electrical devices
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CONCEPT 2 – ENERGY TRANSFERLearning Concept Identify electrical conductors and insulators
Compare resistance of different materials to electric flow
CONCEPT 2 – ENERGY TRANSFER Insulators do not allow for easy transfer of
electrons away from the nucleus Tightly bound to the nuclei
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CONCEPT 2 – ENERGY TRANSFER In a conductor the electrons are more
loosely bound so they can move away from the nuclei Current will only flow if the conductor is hooked
to an electrical source
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CONCEPT 2 – ENERGY TRANSFER Different materials conduct electricity at
different abilities Important to know so devices designed are both
safe and effective
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CONCEPT 2 – ENERGY TRANSFER A resistor is a type of conductor
Allows current to pass but applies a resistance to it Limits amount of electric current to pass
Resistance is a measure of how difficult it is for electrons to flow through a substance
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CONCEPT 2 – ENERGY TRANSFER Resistance is measured in ohms
Symbol is the Greek letter omega, W The more resistance a substance has, the
more energy is gained from each electron passing through it
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CONCEPT 2 – ENERGY TRANSFER A polygraph machine (lie detector) is an
application of resistance Measures skin resistance, blood pressure and
respiration
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CONCEPT 2 – ENERGY TRANSFERLearning Concept Use switches and resistors to control
electrical flow Predict effect of these devices and others in an
application
CONCEPT 2 – ENERGY TRANSFER A switch is the best method for turning
electricity on and off Basic principle: when on, two conductors are
pressed together and electrons can flow When off, the conductors are not in contact,
and electron flow is interrupted
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CONCEPT 2 – ENERGY TRANSFER A variable resistor, or rheostat, is used to
increase or decrease the amount of current in a circuit slowly Dimmer light switch Volumes on stereos Foot-operated speed controls on sewing
machines
CONCEPT 2 – ENERGY TRANSFERLearning Concept Describe, using models, the nature of electric
current Explain the relationship between current,
resistance, and voltage
CONCEPT 2 – ENERGY TRANSFER Recall:
Current looks at how quickly an electrical charge is able to move (amps)
Voltage looks at how much charge is carried in the electrical current (volts)
Resistance is a measure of how difficult it is for electrons to transfer (ohms)
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CONCEPT 2 – ENERGY TRANSFER
CONCEPT 2 – ENERGY TRANSFER The hydo-flow model has several
components Water in the container Amount of water pouring from the spouts Force of gravity on the water Diameter of the spout
CONCEPT 2 – ENERGY TRANSFERLearning Concept Measure voltages and amperages in circuits
Apply Ohm’s law to calculate resistance, voltage and current in simple circuits
CONCEPT 2 – ENERGY TRANSFER German scientist Georg Simon Ohm proved
a mathematical link between voltage (V), current (I) and resistance (R)
CONCEPT 2 – ENERGY TRANSFER Ohm’s law states that as long as
temperature remains the same Resistance of a conductor stays the same Current is directly proportional to the voltage
applied
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CONCEPT 2 – ENERGY TRANSFER So long as two of the three units are known,
the last one can be solved for
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CONCEPT 2 – ENERGY TRANSFER
Ohm’s Law
Quantity Symbol Unit Equation Measured with …
Voltage V volts (V)
Voltmeter
Current I amps (A)
Ammeter
Resistance R ohms (W)
Ohmmeter
CONCEPT 2 – ENERGY TRANSFERExample An electrical stove is connected to a 240-V
outlet. If the current flowing through the stove is 20-A, what is the resistance of the heating element?
CONCEPT 2 – ENERGY TRANSFERExample A 30-V battery creates a current through a
15-Ω resistor. How much current is created?
CONCEPT 2 – ENERGY TRANSFERExample A motor has an internal resistance of 40-Ω.
The motor is in a circuit with a current of 4.0-A. What is the voltage?
CONCEPT 2 – ENERGY TRANSFERExample A current of 625-mA runs through a bulb that
is connected to 120-V. What is the resistance of the bulb?
CONCEPT 2 – ENERGY TRANSFERLearning Concept Develop, test and troubleshoot circuit
designs for a variety of specific purposes
CONCEPT 2 – ENERGY TRANSFER A circuit is simply a complete path that
charged particles can flow through Often drawn with symbols in an image known as
a schematic or a schematic diagram
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CONCEPT 2 – ENERGY TRANSFER Using your textbook as a reference (pg 312)
complete the following diagram of electrical symbols
Symbol Represents DescriptionConductorCellBatteryLampResistorSwitchAmmeterVoltmeterRheostatMotorFuse
CONCEPT 2 – ENERGY TRANSFER A series circuit is one in which the current
passes through each bulb in turn
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CONCEPT 2 – ENERGY TRANSFER
Disadvantages If the pathway is
interrupted the whole circuit cannot function
Adding components increases the total resistance Adding another bulb
would make all the lights dimmer
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CONCEPT 2 – ENERGY TRANSFER Advantages
Household circuits are wired so that it is possible to turn off all the electricity in the circuit
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CONCEPT 2 – ENERGY TRANSFER Parallel circuits have separate current
paths for each section of the circuit Each bulb would have its own path to the current
source
CONCEPT 2 – ENERGY TRANSFER Advantages
An interruption or break in one pathway does not affect the rest of the pathways
Adding extra resistors decreases the total resistance in the circuit
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CONCEPT 2 – ENERGY TRANSFERLearning Concept Identify similarities and differences between
microcircuits and circuits in a house
CONCEPT 2 – ENERGY TRANSFER Define transistor Define fuse
Use page 315 of your textbook to compare and contrast microcircuits and household wiring