Presentation on theme: "Mr Powell 2011 Index What is the link...... Current & Voltage Models AF1 Mr D Powell Understand more about how current and potential difference behaves."— Presentation transcript:
Current & Voltage Models AF1 Mr D Powell Understand more about how current and potential difference behaves in circuits Use and evaluate models of circuits Work as a team in different roles Assessment Focus 1: Thinking scientifically Thread 1: Using models for and in explanations
Mr Powell 2011 Index Mini Whiteboards... Without talking to another or sharing any ideas draw a complete electrical circuit with symbols including... two bulbs, cell, and a switch to turn it on and off. Now draw another one with the same components but make it so that one one bulb can be turned off and the other is on all the time.
Mr Powell 2011 Index Measuring Current Flow... 0.5A 1.0A 1.5A A chemical cell or battery of cells provides a flow of electricity. This flow registers on a meter called an ammeter which counts electrons as they flow through the wires. Can you predict the two other ammeter readings, write it on your board and hold it up....
Mr Powell 2011 Index Measuring Current Flow... 0.3A In a series circuit the current is the same everywhere as electrons push around the circuit like water down a pipe. It all travels at the same speed. Can you predict the other ammeter readings? 0.3A
Mr Powell 2011 Index Voltmeters tell us how much “potential” there is in a circuit. What we mean is the potential for an electron to move. We call this “potential difference” as it is the difference in electrical potential. It is the same thing as gravitational potential but for electrons! If each cell is 1.5V what should the voltmeters read.... Potential Difference 1.5V 4.5V
Mr Powell 2011 Index What is a Coulomb Electrons are charged particles and each of them have a very tiny charge or attractiveness of -1.6 x 10 -19 C. If we add a load of them together and think of them as a single “sphere of charge” or ball we get a whole coulomb of charge and can think about defining the ampere or amp 1A = 1C/s C 1.6 x 10 -19 C x 6.25 x 10 18 electrons = 1C e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e-
Mr Powell 2011 Index Mini whiteboards... Without talking to another or sharing any ideas with another person imagine you met an alien and had to explain what an electron was..... Hold it up when you are finished as quick as you can...
Mr Powell 2011 Index What happens inside circuits... This is a simple current and voltage model... 4V 1A CCCC C C CC C 1J C As the Coulombs of Charge move they release their energy as heat and light (through the bulb) C 1J = 1 Coulomb of charge = 1 Joule of energy = 1 Second of time
Mr Powell 2011 Index Activity – Modelling Circuits... Instructions... Work in a team of 5. Your team will be given some information about an electricity model. It is your job to study this, make a 3D model or diagram and then explain it to the rest of the class. Each team has a different model. At the end you all fill in a grid looking at each model as each team explains to the class. Group Roles 1.Planner: organise team to complete work in allotted time. 2.Presenter: writes some notes to explain model to the class or draws a diagram or table of items to help. 3.Evaluator: watches how team performs and suggests improvements using assessment grid. Tick any boxes achieved. 4.Maker 4&5: lead producing the model
Modelling Electricity One idea to help us explain electricity is to think of a electricity like gravitational potential energy. When you are up high you have lots of it. We can even use diagrams to help us to understand what is going on... transfer to heat energy in resistor Stored chemical energy transfer to heat energy in wires
Circuit Rules Any circuit you can use the idea of the following rules;
Mr Powell 2011 Index Level Descriptions for Assessment Focus 1 – Using models for and in explanations.. Level 3 Make a model to represent something you have seen Level 4 Describe scientific ideas using scientific terms Describe scientific ideas using a physical model Level 5 Explain ideas or events using abstract models Develop a description that uses abstract ideas or models of more than one step Suggest solutions to problems using scientific ideas Level 6 Explain logically ideas or events using abstract models in new situations Say what is good or bad about a model Select the most appropriate model to explain an idea Level 7 Develop original models to explain ideas and events Justify the selection of a model to explain an idea Use language that is ambitious, clear and relevant to the context Level 8 Explain events logically linking different ideas or models beyond the level expected in normal science lessons Explain events explicitly linking different ideas or models Use criteria to evaluate the appropriateness of a model
Mr Powell 2011 Index Level Descriptions for Assessment Focus 1 – Using models for and in explanations.. Level 3Represent things in the real world using simple physical models Level 4Use simple models to describe scientific ideas Level 5 Use abstract ideas or models of more than one step when describing processes or phenomena Level 6 Use abstract ideas or models or multiple factors when explaining processes or phenomena Level 7 Make explicit connections between abstract ideas and/or models in explaining processes or phenomena Level 8 Describe or explain processes or phenomena, logically and in detail, making use of abstract ideas and models from different areas of science
Possible Answers Donkey Model Ski SlopeCentral HeatingLorries & Loads Runners in Race What forms the circuit in this model? TrackSki slope tracksWater PipesRoad NetworkRunning Track What goes round the circuit? DonkeysSkiersWaterTrucksRunners What represents energy in the circuit? Bags of Hay Height of slopes HeatLoad carried Energy level of runner from muscles Where does the current collect energy? BarnSki Lift Boiler / Hot water tank Depot Isotonic Drinks Where does it give up energy? To animals in field As it loses height RadiatorsCustomerSurroundings Which model is better & why?
Printed Materials Mr D Powell Print one set per group. Assessment Focus 1: Thinking scientifically Thread 1: Using models for and in explanations
Ski Slope Model.... Skiers represent the electrons moving in wires current flowing Speed of skiers is the amount of current flowing i.e. 1A Height of mountain is the voltage of the cell or potential difference Skiing pathways are like wires Skiers convert energy as they ski down mountain like a bulb Skiers can take different paths to show resistance Skiers are lifted to top of mountain by ski lift which is like a cell or battery
Donkey Model.... Donkeys move along the farmyard tracks (charges) Gates stop the donkeys They carry bags of hay (energy) to field and other animals to eat When track is wet or muddy Donkey is slowed down Donkeys pick up hay from barn (energy) Donkeys speed is current flow
Trucks Model.... Trucks are like charges moving Traffic lights stop them Amount of current is speed of trucks Trucks deliver goods to customers (energy) Trucks pick up energy at their supply depot (energy) Traffic jams slow them down (resistance)
Central Heating Model.... Water pipes are the wires Boiler/ Hot water tank is like the cell giving energy Water flow is the charges moving Radiators give out heat (energy) like bulbs Flow of water is the current Timer is like a switch for on/off
Water Pump Pipes Radiator Resistor or Bulb Cell Wires Electric Current Electrical Circuit Model...
Runners in Race Model.... Runners are the charges moving Runners recombine to show current at branches Runners speed is the flow of current Runners return to start (cell or battery) Runners can split at branches in parallel circuit Runners lose energy from muscles as they run (energy) Can drink isotonic drink to boost energy Energy lost to surroundings as run
Modelling Current Flow.... Current Flow + Half Current Flow = = Current Recombines Current Splits