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Electric Charges and Currents

Electric Charges and Currents. Atoms and Electricity. All matter is made up of atoms Parts of the atom Protons – positively charged (+) Neutrons – neutral (no charge) Electrons – negatively charged (-) Where are the electrons in an atom? Move freely in the electron cloud

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Electric Charges and Currents

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  1. Electric Charges and Currents

  2. Atoms and Electricity • All matter is made up of atoms • Parts of the atom • Protons – positively charged (+) • Neutrons – neutral (no charge) • Electrons – negatively charged (-) • Where are the electrons in an atom? • Move freely in the electron cloud • Can be added and removed (form ions)

  3. Atomic Model • “Cloud Model”

  4. Atoms and Electricity Attraction between particles that have opposite charges Repulsion between particles that have the same charge Like charges repel each other, opposite charges attract (think about magnets!)

  5. Conductivity • Some materials allow electrons to move through them easily – Conductors – metals • Some materials do not – Insulators – plastic, rubber, wood, glass

  6. Electricity • Objects can develop electric charges when their atoms gain or lose electrons • Friction – rubbing two objects together • Van der Graaf generator

  7. Electricity Conduction – electrons flow from one object to another through direct contact Electrical wires – copper

  8. Investigate Charge Induction • Go to my website • Click on Physical Science Websites • Click on Unit 7 – Balloons and Static Electricity • ClickRun • Uncheck the Ignore Initial Balloon Charge box • Rub the balloon on the sweater and see what happens when you stick it to the wall

  9. Electricity Induction – rearrangement of charges Balloon and paper

  10. Static Electricity • Static electricity is the buildup of electric charges on an object • Once the charges build up, they do not move • The loss of static electricity is called electric discharge • Lightning • “Shocking” someone when you touch them

  11. Lightning

  12. Investigate Static Electricity • John Travoltage • Investigate the effects of different variables on static electricity

  13. Ohm’s Law • Gives us the relationship between voltage, current, and resistance: Voltage = Current x Resistance V = IR Set up the triangle! V I R

  14. Power • Power is calculated: • Power = Voltage x Current • P = VI • The unit of power is watts (W) • Set up the triangle! P V I

  15. Current • Charges (electrons) can flow through a conductor • An electric current is a flow of charge Current (I) is the amount of charge that passes a given point per unit time • Current is measured in amperes or amps, (A)

  16. Current In order to have a current, there must be a potential difference and a circuit Potential difference – the difference in potential between two places – measured in volts (V) Circuit – a closed path through which electrons can flow

  17. Current Remember - thermal energy flows from objects with higher temperatures to objects with lower temperatures This is similar with electricity, except instead of temperatures we have charges Greater Potential Energy  Lesser Potential Energy

  18. Flow of Electricity • When using electricity you want a continuous flow of electrons through whatever you are trying to power. • If you have a potential difference (usually from a wall outlet or battery), all you need is a closed path or circuit through which electrons can flow • The flow of electrons through the circuit is called the current

  19. Flow of Electricity In order to make the charges move and keep moving, you need a device that uses energy to do the work required to move electrical charges Batteries Generators

  20. Batteries • Batteries produce electricity by converting chemical energy into electrical energy

  21. Resistance • The amount of current that can flow through a circuit depends on • Voltage • How the wire resists the flow of electricity • The opposition to the flow of electric charge is called resistance(R) • Resistance is measured in ohms (Ω) • Anything that uses current creates resistance

  22. Circuits Red Blue Yellow Green

  23. Series Circuits • All of the parts of a series circuit are connected one after the other • Only one path for the electrons • If there is a break in the circuit, no current can flow

  24. Parallel Circuits • The different parts of a parallel circuit are on separate branches • Several paths for the electrons • If there is a break in one branch of the circuit, electrons can still move through other branches

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