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# Electricity

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### Electricity

1. 1. Matter• All matter is made of very small particles calledatoms• Atoms are composed of even smaller particlescalled protons (+), neutrons (no charge) andelectrons (-)• The attraction between protons and electrons iswhat holds the electrons in placed around anatom• An atom is neutral if it has the same number ofproton as it does electrons
2. 2. Electricity• Charge – a physical property that can bepositive or negative• Law of electric charge – like chargesrepel, opposite charges attract• Force between charged objects if anelectric field exist is called electric force• 2 things affect electric force:– Amount of charge– Distance between the charges
3. 3. • Electric field is the region around a chargedobject• An object becomes positively charged when itloses electrons and negatively charged when itgains electrons• Objects become charged by friction, conduction,induction• Friction – when electrons are “wiped” from oneobject to another (rubbing your hair with aballon)•
4. 4. • Conduction – electrons move from oneobject to another by contact• Induction – charges in a uncharged metalobject are rearranged without directcontact it a charged object• Electrical conductor – material whichallows charges to move freely• Electrical insulator – material in whichcharges can’t move freely
5. 5. • Static electricity – electric charge at reston an object (static – not moving)• Electric discharge is the loss of staticelectricity as the charge moves off theobject• Electric discharges can happen quicklywith a flash of light, a shock, or a cracklingnoise (lightning)
6. 6. • Electric current is the rate at whichcharges pass a given point (unitsamperes, A)• When a current is established (turned on)an electric field is created so quickly(speed of light) that all electrons startmoving through the wire at the sameinstant
7. 7. • AC – (alternating current) the chargescontinually shift direction (plug outlets)• DC – (direct current) the charges always movein the same direction (battery)• Voltage is difference between two points in acircuit (units volts, V)• Voltage is a measure of how much work isneeded to move a charge between two points,the higher the voltage, the more energy releasedper charge (9V, 12V, 120V, 220V)
8. 8. • Resistance is the opposition to the flow ofcharges (units ohms,Ω (R))• The higher the resistance, the lower thecurrent• Resistance depends on the material,length, thickness and temperature• Superconductor – super cooled materialthat lowers resistance (magnets)
9. 9. • Device can change one form of energy toanother such as thermocouples andphotocells. Thermocouples changethermal energy into electric energy andphotocells change light energy to electricenergy• Electric circuits are complete closed pathsthat allows electric charges to flow
10. 10. • Three parts to a circuit are:• 1. Energy source (provides electriccharge)• 2. Wires (allows charge to flow from pointto point)• 3. Load (changes electric charge intoother forms of energy)• EX: radio – electrical to sound
11. 11. Batteries (power source)Dry Cell Wet Cell
12. 12. • Two types of circuits: series and parallel• Series: all parts are connects in a singleloop in a one way path• All current must pass through thecomplete series for circuit to work• Any interruption causes the circuit to fail(Xmas lights)• Useful in burglar alarms
13. 13. Series Ciruit
14. 14. • Parallel: loads are connected side by sideand current can travel on more than onepath• When circuit is interrupted, circuitcontinues to function regardless• Homes are wired on parallel circuits andcan have different loads in the circuit
15. 15. Parallel Circuit
16. 16. • Circuit failures are usually caused by overloads or damage to the structure of thecircuit• Fuses and circuit breaks “fail over” andautomatically break the circuit to protectcircuit and property
17. 17. • Electromagnets – temporary magnets that losetheir magnetism when electric current isremoved• Electricity can produce magnet fields and cancause metals such as iron and steel to act likemagnets• Generator is a device that converts mechanicalenergy into electrical energy by using magnetsand a coil of wire that creates magnetic fields
18. 18. • Electric motors convert electrical energyinto mechanical energy that is used to dowork• EX: motors in house hold appliances likeblenders and washing machines