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Section 2.0

Section 2.0. Technologies can be used to transfer and control electricity. 2.1 – Controlling the Flow of Electrical Current. Electrical current flows through circuits

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Section 2.0

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  1. Section 2.0 Technologies can be used to transfer and control electricity

  2. 2.1 – Controlling the Flow of Electrical Current • Electrical current flows through circuits • The amount of current that can flow through a circuit is limited by the conductive properties of the components in the circuit

  3. http://videos.howstuffworks.com/discovery/27710-how-do-they-do-it-creating-neon-signs-video.htmhttp://videos.howstuffworks.com/discovery/27710-how-do-they-do-it-creating-neon-signs-video.htm

  4. Conductors and Insulators • In conductors, electrons can move easily because they are not tightly bound to the nuclei of the atoms • In insulators, the electrons cannot move easily

  5. http://www.youtube.com/watch?v=8Pnsbh0DrE4

  6. Superconductors • A superconductor is a material that have no resistance to electron flow • Many materials are superconductive at very low temperatures http://app.discoveryeducation.ca/search?Ntt=superconductors

  7. Using Conductors, Resistors & Insulators • Resistance is a measure of how difficult it is for electrons to flow • Resistance is measured in ohms (Ω) • Resistorsare parts of a circuit that provide high resistance to reduce the amount of current flowing through the circuit • For any given voltage, more current flows through a resistor with a LOW resistance than one through with a HIGH resistance

  8. http://www.bbc.co.uk/bitesize/standard/physics/using_electricity/resistance/activity/http://www.bbc.co.uk/bitesize/standard/physics/using_electricity/resistance/activity/

  9. Devices that use Resistors • The more resistance a substance has, the more the substance gains energy from each electron passing through it. • The energy gained is radiated to its surroundings as either heat or light • Some examples of devices that use resistors are:

  10. http://www.youtube.com/watch?v=t4SP_mYh4wQ • HowStuffWorksHow does a lie detector (polygraph) work

  11. Switches and Variable Resistors • Switches create a break in the circuit that interrupts current flow, therefore controlling the flow of current in the circuit • A variable resistor is another type of control • These resistors (also known a rheostats) allow you to adjust the amount of current flowing through a circuit, rather than simply turning it on or off • This can be done through control knobs or pedals

  12. Topic 2.2 Modeling and Measuring Electricity

  13. Electrical Charge • Electrical charge is measured in Coulombs • This is named after Charles A. Coulomb • 1 coloumb = 6.25 billion billion electrons

  14. 2.2 – Modeling and Measuring Electricity • Voltageis a measure of how much potential energy each electron that flows through a circuit possesses • Voltage is related to both current and resistance in circuits

  15. Ohm’s Law • In 1826, Georg Ohm determined through experiments that voltage (V), current (I) and resistance (R) are mathematically related: • Resistance is measured in ohms (Ω)

  16. Ohm’s Law states that, as long as temperature remains constant: • The resistance of a conductor remains constant • The current is directly proportional to the voltage applied

  17. http://www.youtube.com/watch?v=-mHLvtGjum4 • MAKE presents: Ohm's Law

  18. Applying Ohm’s Law

  19. 2.3 – Analyzing and Building Circuits • Circuit diagrams or schematics are representations of a circuit that is built • Recall that all circuits require four components:

  20. Parallel and Series Circuits • Circuits can be divided into two general types: parallel and series • These circuit types are defined by the number of branches that are present in the circuit • http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/electricity/circuitsact.shtml

  21. Series Circuits • Definition: the current passes through each bulb in turn – there is only one pathway • Diagram:

  22. Parallel Circuits • Definition: have a separate path for each section of the circuit • Diagram

  23. Effects of Multiple Paths in Parallel Circuits • In parallel circuits, adding more resistors in circuits actually will reduce the overall resistance of the circuit • As well, the voltage change in each branch is equal

  24. Applications of Parallel and Series Circuits • Parallel circuits are more commonly used in devices than series circuits • Imagine what would occur if your house used series circuits instead of a number of parallel circuits…

  25. Transistors • In tiny consumer electronics, transistors are used instead of conventional switches • Transistors are made of three layers of silicon sandwiched together • These transistors have no moving parts and operate on digital code running through the middle layer of the transistor to control the movement of current through a circuit

  26. Microcircuits • Are also called integrated circuits • Are made up of microscopic transistors and resistors • It is a circuit on an extremely small scale

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