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Transcript
Ms. Bodnar Chapter Two Chapter Two: Technologies Can Be Used to Transfer and Control Electrical Energy 2.1 Controlling the Flow of Electrical Current • Neon Lights as a Circuit: ▫ Electricity must travel all the way through the tube to make neon gas glow ▫ Sign must be equipped with on/off switch ▫ Must be contained so no accidental electrocution A Unique Circuit • These neon lights are tubes filled with different types of gases (gas is the conductor), metal terminals are on either end of the tube; thereby, ____________________________ _________________________________. • Neon gas is an insulator by when current is applied atoms get excited and they free themselves from the atom Conductors and Insulators • Insulators- electrons are tightly bound to the nucleus = less likely to break away • Conductors- electrons loosely bound to nucleus = more likely to break away ▫ When you apply a voltage, ____________________________________________ __________________________________________________________________ __________________________________________________________________ Unit D: Electricity Science 9 1 Ms. Bodnar Chapter Two Superconductors • ___________________________________________- perfect conductors, they have no resistance to electron flow • Discovered by Heike Kamerlingh Onnes ▫ • At - 273oC, mercury is a superconductor ___________________________- allows electric current to pass, but provides resistance to it (limits the amount of current going through) • _____________________________- measure of how difficult it is for electrons to flow through a substance • ____________________________- the measure of resistance (Ω) Solutions as Resistors • Solutions can conduct electricity as long as they have a conducting solute • Minerals in water gives water the ability to conduct electricity Polygraph Machine • Measures skin resistance, blood pressure, and respiration • When lying those factors will cause a spike on the computer screen due to an increase in resistance How do Switches Work? • When the switch is on the two conductors are pressed together thereby completing the circuit • When the witch is off the two conductors aren’t touching = no circuit Doorbell Unit D: Electricity Science 9 2 Ms. Bodnar Chapter Two Variable Resistor or Reostat • ____________________________- resistor whose resistance can be changed by adjusting the portion of the resistor the current travels through • This will increase or decrease the amount of current in the circuit by adjusting the portion of the resistor that current travels through. Check and Reflect: Page 303 #1-10 Unit D: Electricity Science 9 3 Ms. Bodnar Chapter Two 2.2 Modeling and Measuring Electricity • Electricity needs a source if it is going to supply energy to different places. The stronger that source is, the stronger the electricity is going to be. • Electricity will not flow without a difference in electrical potential (will flow from high to low) • Higher voltage coming from power station will have more electrical potential energy Resistance and Current • Current ___________________________________________________________ in a circuit (smaller pipe = less flow) • Interrupt the path = more resistance = less current Unit D: Electricity Science 9 4 Ms. Bodnar Chapter Two Ohm’s Law • States that as long as temperature stays the same: ▫ _________________________________________________________________ ▫ _________________________________________________________________ (current = voltage) Using Ohm’s Law Examples: A 30 V battery creates a current through a 15 Ω resistor. How much current is created? Unit D: Electricity Science 9 5 Ms. Bodnar Chapter Two 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? A current of 625 mA runs through a bulb that is connected to 120 V. What is the resistance of the bulb? Unit D: Electricity Science 9 6 Ms. Bodnar Chapter Two Using Test Meters • _____________________________– instruments for measuring potential difference in volts • • ▫ Voltage Drop- potential difference across a resistor or device ▫ Millivoltmeters- used to measure small voltages _____________________- used to measure electrical currents in amperes ▫ How many electrons pass through the circuit each second. ▫ Galvanometers- meters used to measure small currents _______________________________- you can measure any of the variables: voltage, current, or resistance. ▫ Make sure you select the right variable Types of Resistors • Depends on how much voltage goes through them • ____________________________________: wire made of heat-resistance alloy wrapped around an insulating core (0.1 Ω to 200 Ω) • ____________________________________: made of carbon mixed with other materials. Cheaper to make but less precise (10 Ω to 20 Ω) Check and Reflect: Page 310 #1-10 Unit D: Electricity Science 9 7 Ms. Bodnar Chapter Two 2.3 Analyzing and Building Electric Circuits • _________________________________- there are special symbols that are for certain parts of a circuit. • _________________________________- drawing made with special circuit symbols. • Parts of a circuit: ▫ ________________________________ (energy and electron supply), ▫ ________________________________ (path for current), ▫ ________________________________ (controls current flow), ▫ ________________________________ (converts to another form of electricity) Unit D: Electricity Science 9 8 Ms. Bodnar Chapter Two Circuit Analysis: Bulldozer Series Circuit • Series circuit- ____________________________________________________________ ________________________________________________________________________ • One path...if interrupted, no flow • More light bulbs = more resistance = decrease current = dimmer lights Parallel Circuit • Parallel circuits- __________________________________________________________ ________________________________________________________________________ • Interruption in one path will not affect the other ▫ This means that there is little resistance therefore all light bulbs will remain the same intensity Unit D: Electricity Science 9 9 Ms. Bodnar Chapter Two Applications of Series and Parallel Circuits 1. __________________________________________- use parallel circuits. Why? 2. ______________________________________________- circuit made up of miniaturized components, especially an integrated circuit (circuit of inseparable, often microscopic, components formed on the surface of a single piece or chip of semiconductor crystal, usually silicon) a. ____________________________________- solid-state components because they are made of solid material with no moving parts...three layers of silicon (middle layer acts as a switch) Check and Reflect: Page 316 #1-11 Page 317 #1-9 Unit D: Electricity Science 9 10