22 Current The flow of electrons through a wire or a conductor. SI unit = (Amps) A
23 2 types of current A/C – alternating current D/C – direct current ie: by plugging into thehousehold wiringD/C – direct currentie: batteries
24 ConductorDEFINITION: Material that allows electrons to move easily through it.IN OTHER WORDS: Just like a train conductor moves cars from one track to another track, conductors move electrons from one place to another.
25 Which metal is the best conductor for your internet connection?
27 InsulatorDEFINITION: Material that does not allow electrons to move through it.IN OTHER WORDS: Just as a potholder insulates you from heat, electrical insulators slow down or resist the flow of electricity.
37 To sum them up….. silver glass copper rubber gold oil aluminum asphalt Conductors:silvercoppergoldaluminumironsteelbrassbronzemercurygraphitedirty waterconcreteInsulators:glassrubberoilasphaltfiberglassporcelainceramicquartz(dry) cotton(dry) paper(dry) woodplasticairpure water
38 Mini Quiz The build up of charges on an object is called? Electrons do not move through…Electrons move easily through materials called …Static ElectricityInsulatorsConductors
39 ResistanceDEFINITION: the tendency for a material to oppose the flow of electrons, changing energy into thermal energy and light.SI unit = Ohm’s (W)See pg Fig. 8
40 What effects resistance? TemperatureThicknessLength
41 Think of a common household item that has a resistor Something weuse in class?
42 Potential Difference - Voltage DEFINTION: Difference in potential between 2 different places.IN OTHER WORDS:It is the amount of work that must be done to carry a charge from one point to another.
43 A source of potential difference must keep the current flowing.
44 Ohm’s Law Potential difference = current x resistance V (volts) = I (amperes) x R (ohms)Compare to: Water in a HoseElectricity is:DC in a WireElectrical UnitsSymbolpressurepotential (V)VoltsVrate of flowcurrent (I)Amps (or Amperes)Africtionresistance (R)OhmsW
45 How do you remember the formula? …..if this helps, use it.
47 Practice problems resistance – R = 75 ohms voltage – V = 110 volts A 75 ohm circuit is powered by a 110-Volt energy source. What is the current flowing in this circuit?First we identify the information that we are given in the problem:resistance – R = 75 ohmsvoltage – V = 110 voltsNeed to know amps110V = I x 75 ohms (rearrange formula)Amps = 110 volts / 75 ohms (W)1.5A
48 Practice problems resistance = 250 ohms current = 0.95 amps What is the voltage of a circuit with a resistance of 250 ohms and a current of 0.95 amps?First we identify the information that we are given in the problem:resistance = 250 ohmscurrent = 0.95 ampsNeed to know voltsV= 250 ohms x 0.95 ampsVolts = 250 ohms x 0.95 amps237.5V
49 Mini Quiz ___ is a flow of electrons thru a wire or conductor. Current A current must have a constant flow of ___CurrentPotential Difference
50 Mini Quiz Tendency for a material to oppose the flow of electrons What 3 quantities are related to Ohm’s LawResistanceVoltage, current, and resistance
51 Review Quiz of 20.2 before next section View here
65 Mini Quiz A _____ is a closed path in which electrons flow Circuit Christmas lights are an example of …..Household wiring are wired by …CircuitSeries CircuitParallel Circuits
66 Number your paper 1-9. View here Video quizNumber your paper 1-9.View here
67 Check your answers 9. Swimming pool 1. c) electrons Open area Climbing on a metal ladderFishing in a metal boat on a lakeStanding in a field wearing a metal suit1. c) electrons2. a) nucleus3. b) insulators4. c) electrical5. b) attract6. c) positive7. b) neutral8. d) negative