Electricity:

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Electricity
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Using electricity

• In 1771, Luigi Galvani discovered that the
  muscles of dead frogs twitched when struck by a
  spark
• May have inspired the idea behind the story
  Frankenstein

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How do we get Electricity?
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How to generate electricity
Generation of Electricity Coil of Wire  
Magnetism   Relative Motion
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How does an electric system work?

• The basic components are
• Power Plant Electricity is produced here
• Power Grid A network that connects power plants
  to substations and substation to homes.
• Transmission Substation Transformers increase
  voltage so that volts can be sent over long
  distances.
• Distribution Substation Transformers reduce
  voltage to a level suitable for the surrounding
  community
• Distribution System Delivers electricity to
  homes and businesses. Line may be a underground
  or overhead.
• Service Connection Connection of customers to
  the grid. A meter is connected also to measure
  the amount of electricity used by customers

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Electrical Flow

• When you switch something on, you complete a
  pathway for electricity to flow through.
• The pathway that allows electrical energy to flow
  is called an electric circuit.
• Electric circuits consist of three components
• A Power Supply Provides electrical energy
• A Load Converts electrical energy into another
  form
• A Conducting Path Allows electric charge to flow
  around the circuit.

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Electric Circuits

• Electric circuits consist of three components
• A Power Supply Provides electrical energy
• A Load Converts electrical energy into another
  form
• A Conducting Path Allows electric charge to flow
  around the circuit.

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A simple electric circuit
Power Supply
Load
Conducting Path
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Circuit Diagram symbols



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Current

• Current measures the amount of charge flowing
  through a circuit .
• A large current has more charge flowing every
  second than a small current.

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Measuring Current

• Current is measured in a unit called ampere (A)
  or amps
• Milliamps (mA) are used to measure small
  currents.
• Current can be measured using a device called an
  ammeter.
• Ammeters need to be inserted into the circuit to
  get a reading.

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Measuring Voltage

• Voltage is measure in Volts (V)
• A device that measures the amount of volts
  passing through a circuit is called a voltmeter

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Voltage

• Voltage is a measure of the amount of energy
  there is to push charge through a circuit.
• Voltage is supplied by batteries, power packs and
  power points.

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Energy Sources
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Energy Sources

• Batteries, power packs or power points are all
  considered energy sources.
• They provide all the electric energy and voltage
  to a circuit.
• Energy sources create an electric field that
  pushes electrons around a circuit.

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Power points and power packs

• Power points supply approximately 240 volts into
  your home
• Power packs like the ones we use in class supply
  up to 12 volts
• The power for which is produced in a variety of
  power plants.

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Batteries

• Batteries are used when we need portable energy
  sources.
• 1 AA battery provides 1.5 volts
• While car batteries provide 12 volts
• Batteries are made up of cells.
• These cells can be either wet or dry.

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Wet Cell

• In this wet cell, zinc reacts with the acid and
  releases electrons.
• If a circuit is connected to the plates then the
  electrons will flow to the copper plate
• As they flow through the circuit the globe will
  light.
• Wet cells are usually large and heavy and can
  leak acid if tipped over.

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Example Wet Cell.

• A car battery is a collection of wet cells.
• The wet substance is sulfuric acid
• The plates are made of lead and lead oxide.
• While a car is running it reverses the chemical
  reaction recharging the battery.
• Eventually chemicals build up on the plate and
  the batter dies.

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Dry Cell

• Being large and heavy wet cells are useless for
  small devices like
• Ipods
• Laptops
• Remotes
• They use small portable cells called dry cells.
• Dry cells contain a chemical paste and their
  electrodes are designed to save space.
• It is common that several batteries are connected
  together to supply more voltage.

4.5 volts
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Photovoltaic Cell

• A photovoltaic cell (or solar )is made up of two
  layers.
• These two layers are semiconductors.
• When sunlight strikes the top layer electrons are
  given energy to move to the bottom layer.
• This creates an electric current.

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The Living Battery -Electrophorus Electricus

• Aka the electric eel
• Actually a freshwater fish.
• It can produce up to 600 volts
• This is five times the amount found in an
  electrical outlet
• Uses the electric field to stun fish and to see

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Activity Virtual solar race challenge

• http//wsc.pv.unsw.edu.au/
• This website allows you to build and name a
  virtual solar powered car
• You are then able to race it against computer
  generated cars.

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Activity Virtual solar race challenge

• The important feature of this game is the design
  process.
• You have a limited budget of 240,000 to build
  your car.
• You need to decide on what balance of components
  are important for speed and power.

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Conductors and Insulators
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Conductors

• A conductor is a substance that allows current to
  flow through it easily.
• Examples are metals like
• Copper used commonly in electric circuits
• Aluminium More expensive, used when copper is
  unsuitable.

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Insulators

• Materials that do not allow current to pass
  through them are called Insulators.
• Examples of insulators
• Plastic
• Rubber

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Activity What is a Superconductor ?

• Brief research assignment.
• What are superconductors ?
• What uses are there for superconductors?
• Briefly describe how they work.
• Useful links
• http//superconductors.org/INdex.htm
• http//science.howstuffworks.com/question610.htm

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Energy Users
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Not all metals conduct the same

• All metals conduct electricity, but some do so
  better than others.
• Tungsten and nichrome for example are not very
  good at conducting electricity.
• Therefore electricity flows easier in copper
  wires than in tungsten.
• This is called resistance.

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Resistance

• Resistance converts electrical energy into heat
  and light.
• This is used in light globes with tungsten
  filaments.
• Conductors have a low resistance
• Insulators have a high resistance

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Short Circuit!

• Without any resistance (such as a globe or
  heating element) too much current can flow
  through a circuit.
• This may generate too much heat in connecting
  wires or the energy source.
• This might damage the circuit causing it to melt
  or catch fire!
• This is known as a Short Circuit

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Using Circuits
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Series circuits

• If two globes are arranged in a single line then
  they are said to be in series.
• Although the current is said to each globe is the
  same, the voltage is shared between the two.
• This means that the globes will both glow more
  dimly.
• If one of the bulbs is removed or blows then
  the other globes in the circuit will not light
  up.

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Parallel circuits

• If two globes are arranged in separate branches
  of a circuit then the are said to be in parallel.
  
• Each globe has the same amount of energy and
  voltage supplied to them .
• The current is divided between them,
• This means that they will glow with the same
  brightness
• Also if one globe is removed from this circuit
  the other will still remain lit.

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Examples Fairy Lights

• SERIES

• Parallel

• In a parallel circuit all lights are powered by a
  low voltage source. A transformer reduces the
  voltage from 240 volts to 12 volts. All globes
  receive 12 volts.
• Advantages
• If one globes breaks all the other globes still
  have power.
• This makes it easier to find the broken globe.

• A series circuit arranged of 20 lights would
  share 240 volts from a power point.
• Therefore each globe receives 12 volts.
• Disadvantages
• If one globes broke then all the other globes
  with also go out
• This would make it difficult to find the bad
  globe.

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Comparison of Series and Parallel
Type of Circuit Voltage Current
Series Split Normal
Parallel Normal Split
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Complex circuits

• Circuits can be combinations of series and
  parallel sections.
• Current will always take the easiest way through
  a circuit.
• A section with a single globe will be easier to
  travel on than a section with two.
• Also it will carry twice as much current.

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Household Circuits

• Electrical wiring within you house is one big
  parallel circuit
• Electrical companies supply 240 volts to your
  house.
• Each power point creates an extra parallel
  section that receives the same 240 volts.

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AC/DC

• Direct Current (DC)
• When the current flows in only one direction.
• An example of this is a battery.
• Alternating Current (AC)
• Current flows backwards and forwards.
• Energy is supplied to houses like this because it
  is easier to generate and transmit.

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Electrical Safety.
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When something goes wrong
What's wrong here?

• Short circuits occur when an easier path for
  current is created.
• A huge current flows through causing the circuit
  to overheat and melt.
• You could even become part of the circuit and be
  shocked or electrocuted!
• To prevent this home circuits have fuses or
  circuit breakers.

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Fuses

• A fuse is a thin metal wire, that breaks when too
  much current passes through it.
• Fuses are rated according to the amount of
  current that causes them to melt.
• Therefore a 5 amp fuse will melt at a current of
  5 or more amps.

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Circuit Breakers

• Fuses used to be the most common method for
  protecting circuits within a house.
• These days new houses are built with circuit
  breakers instead.
• Circuit breakers are special switches that trip
  (turn off) the circuit if too much current flows
  through.

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Electric Shock

• Electric shock and electrocution (death by
  electricity) will occur if current finds a path
  through the body.
• Only a small current can cause death.
• The current damages your tissues and interferes
  with the electric signals that drive the heart
  and the brain.

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Idiots and Electricity
Step 1 Climb electrical pole.
Step 2 Reach out and touch high voltage
conductor.
Step 3 16,000 volt Human fireball!
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Electrical Burns
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Emergency Procedures

• If you find someone who has collapsed from an
  electric shock
• Call OOO
• Switch off main power (if possible)
• Do not touch the person (otherwise you will get
  shocked)
• You may be able to move the person if you use an
  insulating material (plastic rope, garden hose)

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The Electric Chair

• The electric chair was invented to replace
  hanging as a method of execution.
• It was intended to be a quick and painless
  alternative
• In the first ever electric chair execution 1000
  volts were applied.
• This burnt skin and burst blood vessels
• It still took another 70 seconds at 1300 volts to
  kill the prisoner.
• Other prisoners convulsed so violently they broke
  their own arms and legs.
• So really its not all that quick and painless !

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The future of electronics
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The Future of electronics ?
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The Future of electronics ?
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Current Technology
Tour Guide Robot - Toyota
Geminoid HI-1 -Hiroshi Ishiguro
Asimo - Honda
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Asimo

• ASIMO stands for Advanced Step in Innovative
  Mobility
• ASIMO is a humanoid robot created by Honda motor
  company.
• Height 130 cm Weight 54 Kg
• By the end of 2007 there were only 46 ASIMO
  robots in existence.
• Further Information
• http//world.honda.com/ASIMO/

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ASIMO evolution

• ASIMO has been in the making for 20 years
• In the picture above you can see the current
  ASIMO compared to its previous versions

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Geminoid HI-1

• Geminoid HI-1is a robotic replica of Professor
  Hiroshi Ishiguro.
• Professor Ishiguro can operate Geminoid from a
  distance.
• This allows him to give two lectures
  simultaneously at universities that are Kms
  apart.
• Further Resources
• http//www.irc.atr.jp/Geminoid/overview.html

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Activity Science at work

• Research a REAL robot
• Create a presentation for the entire class
• The selection of the robot is up to you
• The form of the presentation is also up to you
• Or make a Timeline of Robot development

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Activity Design a Robot

• Individually you are to design a robot to fulfil
  a specific function.
• You must include a design of your robot with
  labelling to explain why each section is
  essential to its function.
• You must also create a short comic strip that
  demonstrates your robot in action.