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Electricity The flow of charges

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Atoms MMade up of: Nucleus: Protons and neutrons Electrons: negative charge orbit nucleus

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Current Flow of electrons Measured in Amperes (Amps) Electrons passing per second

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Circuit Must have complete, unbroken path for current to flow 3 Parts: 1.Load: device run by electricity 2.Wires: path for electron flow 3.Source: moves the electrons through the wire Battery, generator, wall socket (power plant)

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A break in the circuit stops electricity from flowing

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Conductors Materials allowing electrons to flow Examples: metals: electrons loosely held, move easily Copper is one of the best

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Insulators Do not allow electricity to flow Examples: rubber, plastic Electrons held tightly, will not move easily

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Voltage Measures the force “pushing” electrons Volt (v) as unit Higher voltage is higher potential to push electrons through circuit

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WWater dam Lower Potential energy =Low voltage Higher Potential energy=high voltage

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Resistance Force working against (“resisting”) the flow of electrons Measured in Ohms (Ω) All parts of circuit “slows the flow”

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Ohm’s Law Tells how current, voltage, resistance are related Current = voltage resistance I = V R

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Practice Ohm’s Law AA 9 volt battery is used to light 3 bulbs with a resistance of 0.5 Ω each. Wires and a switch add another 3 ohms of resistance. How much current (amps) is flowing through the circuit? Plan WWhat information is given? 99 volts, 3 bulbs x 0.5 ohms = 1.5 ohms plus 3 ohms for total of 4.5 ohms. What formula do I use? II = v / r II = 9 v / 4.5 Ω Solve II = 2 amps Check:Does it make sense? TThe current is less than the voltage because the resistance is reducing the flow

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Circuits and Current Direction

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Series Circuit Only one path for electricity to flow What happens if one bulb goes out? Will the bulbs be dimmer or brighter than a parallel? Load (bulb) Switch

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Parallel circuit More than one path for electricity to flow Each load on separate circuit What happens if one bulb goes out? Compare series/parallel to water supply

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Current Direction CCurrent always flows in one direction: From negative to positive AC vs. DC

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Direct Current DC Charges always flow in same direction, from negative terminal to positive terminal Battery (cells)

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Cells and Batteries CConvert chemical energy to electrical energy Potato clock Electron acceptor Electron donor anode collector plastic seal anode plastic sleeve steel jacket Case sleeve Cell straps Negative terminal Positive terminalelectrolyte cathode collector cathode 9 Volt Battery

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Other sources of DC Thermocouple: convert heat to electricity Solar cells: convert solar energy to electricity

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Alternating Current AC Charges flow from negative to positive but switch directions back and forth (alternate) House current

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Producing AC current IInduction: Coil of wire and magnet produce electricity IIt’s electro-magnetism! Generator: converts mechanical energy to electrical energy Motor: converts electrical energy to mechanical energy

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Electromagnetism Magnetism and Electricity are closely related Electric current causes magnetic fields Cell phones, television, light Magnets can cause an electric current to flow Generators

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Power Measures how fast energy is transferred from one form to another Measured in Watts Power = voltage x current P= V I A 100 watt light bulb changes or uses electrical energy to light energy twice as fast as a 50 watt bulb Brainpop on current Brainpop on current

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