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1-1 ELECTRIC CHARGE -ALL MATTER IS MADE UP OF ATOMS. ATOMS OF THE SAME SUBSTANCE ARE THE SAME. -WITHIN AN ATOM THERE ARE PROTONS, ELECTRONS, AND NEUTRONS (EXCEPT HYDROGEN). -THE PROTONS AND NEUTRONS ARE FOUND IN THE NUCLEUS, WHILE THE ELECTRONS ARE FOUND IN THE ELECTRON CLOUD OUTSIDE THE NUCLEUS. -BOTH PROTONS AND ELECTRONS HAVE A CHARGE. PROTONS (+), ELECTRONS (-). NEUTRONS HAVE NO CHARGE. -PROTONS AND ELECTRONS USED THEIR CHARGES TO EXERT A FORCE. A FORCE IS A PUSH OR PULL ON AN OBJECT. -A FORCE OF ATTRACTION EXISTS BETWEEN OPPOSITELY CHARGED PARTICLES. (PROTON + ELECTRON) - A FORCE OF REPULSION EXISTS BETWEEN PARTICLES OF THE SAME CHARGE. (PROTON + PROTON) -THIS ATTRACTION OR REPULSTION OCCURS BECAUSE THERE ARE ELECTRIC FIELDS SURROUNDING CHARGED PARTICLES. -AN ELECTRIC FIELD IS AN AREA OVER WHICH AN ELECTRIC CHARGE EXERTS A FORCE. IF AN OBJECT COMES INTO AN ELECTRIC FIELD, IT WILL EITHER BE PUSHED OR PULLED. THE STRENGTH OF THE ELECTRIC FIELD DECREASES AS YOU MOVE AWAY FROM THE CHARGED PARTICLE. DO 1-1 SECTION REVIEW ON PAGE 14 #1-4 1-2 STATIC ELECTRICITY -AN ATOM HAS EQUAL AMOUNTS OF PROTONS AND ELECTRONS IN IT WHICH MAKES IT ELECTRICALLY NEUTRAL. HOW THEN, DOES AN OBJECT DEVELOP AN ELECTRIC CHARGE? IT CAN BY EITHER GAINING OR LOSING ELECTRONS. -ELECTRONS ARE FREE TO MOVE, AND ARE EASILY SEPARATED FROM THEIR ATOMS. WHEN AN OBJECT COMES IN CLOSE CONTACT TO ANOTHER OBJECT, ELECTRONS MAY BE LOST, THEREFOR, GIVING IT A POSITIVE ELECTRIC CHARGE. -AN ATOM GAINS AN ELECTRON IT WILL HAVE A NEGATIVE ELECTRIC CHARGE. THESE CHARGED PARTICLES ARE CALLED IONS. -THERE ARE 3 WAYS TO CHARGE A PARTICLE: 1. FRICTION – WHEN 2 OBJECTS RUB TOGETHER. 2. CONDUCTION – ELECTRONS FLOW THROUGH ONE OBJECT TO ANOTHER USING DIRECT CONTACT. 3. INDUCTION – THE REARRANGEMENT OF ELECTRIC CHARGES WITHOUT TOUCHING A CERTAIN MATERIAL. IT ONLY HAS TO COME CLOSE TO IT. -METALS ARE GOOD CONDUCTORS AND ALLOW ELECTRONS IN ATOMS TO MOVE FREELY. SILVER = BEST CONDUCTOR, COPPER, ALUMINUM, MERCURY = GOOD CONDUCTORS. -INSULATORS DO NOT ALLOW ELECTRIC CHARGES TO FLOW FREELY. RUBBER, GLASS, WOOD, PLASTIC, AIR = GOOD INSULATORS -STATIC ELECTRICITY IS THE TRANSFER OF ELECTRONS FROM ONE OBJECT TO ANOTHER WITHOUT FURTHER MOVEMENT. IT IS THE BUILDUP OF ELECTRIC CHARGES ON AN OBJECT. -ELECTRIC DISCHARGE (LIGHTNING) IS THE LOSS OF STATIC ELECTRICITY AS THE ELECTRIC CHARGES MOVE OFF AN OBJECT. -WHEN LIGHTNING OCCURS, THE CLOUD IS NEGATIVELY CHARGED NEAR THE EARTH. IT THEN CHARGES THE EARTH BY INDUCTION. ELECTRONS THEN JUMP FROM THE CLOUD TO THE EARTH, THERBY CAUSING A SPARK. -ELECTRONS CAN ALSO JUMP FROM CLOUD TO CLOUD. THIS GIVES OFF LARGE AMOUNTS OF HEAT. THE RAPID HEATING AND EXPANSION OF THE AIR CAUSES THUNDER. -AN ELECTROSCOPE IS AN INSTRUMENT THAT DETECTS AN ELECTRIC CHARGE. IT HAS A METAL ROD WITH A KNOB AT THE TOP AND A PAIR OF THIN METAL LEAVES AT THE BOTTOM. WHEN IT IS UNCHARGED THE LEAVES HANG STAIGHT DOWN. -WHEN A NEGATIVELY CHARGED OBJECT TOUCHES THE KNOB, BOTH LEAVES BECOME NEGATIVE AND REPEL EACH OTHER AND MOVE APART. -WHEN A POSITIVELY CHARGED OBJECT TOUCHES THE KNOB, THE ELECTRONS ARE TAKEN AWAY AND CREATE POSITIVELY CHARGED LEAVES. THEY REPEL EACH OTHER AND MOVE APART. DO 1-2 SECTION REVIEW ON PAGE 22 #1-4 1-3 THE FLOW OF ELECTRICITY -ENERGY IS THE ABILITY TO DO WORK. -A DEVICE THAT CHANGES OTHER FORMS OF ENERGY INTO ELECTRICAL ENERGY CAN PRODUCE A CONTINUING FLOW OF ELECTRIC CHARGES. FOR EXAMPLE: BATTERIES, THERMOCOUPLES, PHOTOCELLS. -A BATTERY IS A DEVICE THAT PRODUCES ELECTICITY BY CONVERTING CHEMICAL ENERGY INTO ELECTRICAL ENERGY. -IT IS MADE UP OF ELECTROCHEMICAL CELLS WHICH CONTAIN ELECTRODES AND ELECTROLYTES. THE ELECTROLYTE IS A MIXTURE OF CHEMICALS THAT PRODUCES A CHEMICAL REACTION AND RELEASES ELECTRIC CHARGES FROM THE ELECTRODES. -ELECTRIC (ELECTROCHEMICAL) CELLS CAN EITHER BE DRY CELLS OR WET CELLS DEPENDING ON THE ELECTROLYTE. A WET CELL HAS A LIQUID (CAR BATTERY), A DRY CELL IS A SOLID (FLASHLIGHT). -THE ELECTROLYTE DISSOLVES THE ZINC (METAL) AND LEAVES ELECTRONS BEHIND ON THE ZINC ELECTRODE, GIVING IT A NEGATIVE CHARGE. -AT THE SAME TIME THE SAME REACTION IS OCCURING TO THE CARBON (NON-METAL) BUT ELECTRONS ARE BEING PULLED OFF THE CARBON ELECTRODE, GIVING IT A POSITIVE CHARGE. -THE DIFFERENCE IN OPPOSITE CHARGES ON THE ELECTRODES ALLOWS THE FLOW OF ELECTRONS. THIS DIFFERENCE IN CHARGE IS CALLED A POTENTIAL DIFFERENCE. THE GREATER THE POTENTIAL DIFFERENCE, THE FASTER THE FLOW OF ELECTRONS. -A THERMOCOUPLE IS A DEVICE THAT PRODUCES ELECTRICAL ENERGY FROM HEAT ENERGY. IT RELEASES ELECTRIC CHARGES AS A RESULT OF TEMPERATURE CHANGES. THEY ARE USED IN CAR THERMOMETERS TO SHOW ENGINE TEMPERATURE. -PHOTOCELLS CONVERT SUNLIGHT TO ELECTRICAL ENERGY. WHEN LIGHT SHINES ON A METAL SURFACE, ELECTRONS ARE EMMITED. THESE ELECTRONS WERE GATHERED IN WIRE TO CREATE A CONSTANT ELECTRIC FLOW. -ELECTRIC CURRENT IS A FLOW OF ELECTRONS. IT IS THE RATE AT WHICH CHARGE PASSES A GIVEN POINT. A COMPLETE PATHWAY OF ELECTRIC CHARGE, WHICH INCLUDES WIRE AND TERMINALS, IS CALLED A CIRCUIT. -THE SYMBOL FOR CURRENT = I. -THE UNIT IN WHICH CURRENT IS EXPRESSED IS THE AMPERE = A. -AN AMPERE IS THE AMOUNT OF CURRENT THAT FLOWS PAST A CERTAIN POINT PER SECOND. AMMETERS AND GALVANOMETERS MEASURE CURRENT. -CHARGE FLOWS THROUGH A WIRE BECAUSE IT IS A METAL AND A GOOD CONDUCTOR. IT HAS THIS ABILITY BECAUSE ITS ELECTRONS ARE LOOSELY HELD. WHEN A WIRE IS CONNECTED TO A SOURCE THE POTENTIAL DIFFERENCE CAUSES THE ELECTRONS TO BE PULLED AWAY AND FLOW THROUGH THE MATERIAL. -VOLTAGE (VOLTS) IS A TERM THAT IS USED TO DESCRIBE POTENTIAL DIFFERENCE. THE SIZE OF THE POTENTIAL DIFFERENCE DETERMINES THE CURRENT THAT FLOWS THROUGH IT. A VOLTMETER MEASURES VOLTAGE. -THE GREATER THE POTENTIAL DIFFERENCE, THE FASTER THE CHARGES WILL FLOW. -THE SYMBOL FOR VOLTAGE = V. -VOLTAGE IS USED IN YOUR PHYSICAL SURVIVAL AS WELL. A POTENTIAL DIFFERENCE EXISTS ACROSS THE SURFACE OF YOUR HEART. THIS CAN BE OBSERVED ON A MONITOR AND RECORDED AS AN ELECTROCARDIOGRAM (EKG). AN EKG HELPS TO LOCATE DEFECTS IN THE HEART. MUSCLES MOVEMENT IS ALSO A PRODUCT OF POTENTIAL DIFFERENCE. -ELECTRIC EELS PRODUCE JOLTS OF ELECTRICITY UP TO 650 VOLTS TO DEFEND ITSELF OR TO HUNT. STINGRAYS HAVE UP TO 200 VOLTS TO DO THE SAME. TO PUT THIS INTO PERSPECTIVE…120 VOLTS POWERS EVERYTHING IN YOUR HOUSE. -RESISTANCE IS THE OPPOSITION TO THE FLOW OF ELECTRIC CHARGE. THE AMOUNT OF CURRENT THAT FLOWS THROUGH A WIRE DEPENDS ON VOLTAGE AND RESISTANCE. THE SYMBOL FOR RESISTANCE = R. -THE RESISTANCE OF A WIRE DEPENDS ON THE MATERIAL OF WHICH IT WAS MADE. THE LONGER THE WIRE, THE HIGHER THE RESISTANCE. -THE HIGHER THE RESISTANCE OF A WIRE, THE LESS CURRENT FOR A GIVEN VOLTAGE. THE UNIT OF RESISTANCE IT’S THE OHM = Ω. -DIFFERENT WIRES HAVE DIFFERENT RESISTANCES. COPPER HAS LESS RESISTANCE THEN IRON AND THEREFOR IS A BETTER CONDUCTOR. -RESISTANCE IS NOT A BAD THING. IT IS ACTUALLY NECESSARY. LIGHTBULBS GIVE OFF LIGHT AND HEAT DUE TO THE RESISTANCE OF THE METAL FILAMENT. THE FILAMENT IS A VERY THIN PIECE OF METAL THAT RESISTS THE FLOW OF ELECTRICITY WITHIN IT. THIS SAME METHOD IS USED FOR TOASTERS. -TEMPERATURE CAN AFFECT RESISTANCE AS WELL. HIGHER TEMPERATURES INCREASE RESISTANCE BECAUSE THE ATOMS OF A SUBSTANCE ARE MOVING AROUND MORE AND THEY GET IN THE WAY OF THE FLOW OF ELECTRIC CHARGES. -AT VERY LOW TEMPERATURES THE RESISTANCE OF SOME METALS BECOMES ALMOST ZERO. THESE METALS IN THIS STATE ARE SAID TO BE SUPERCONDUCTORS. ALMOST NO ENERGY IS WASTED IN THIS STATE TO HEAT. ALTHOUGH, A LOT OF ENERGY MUST BE USED TO KEEP THE MATERIAL COLD ENOUGH TO SUPERCONDUCT. -THIS KNOWLEDGE CAN ALLOW US TO USE SUPERCONDUCTORS TO MAKE CERTAIN MAGNETS FLOAT IN MID-AIR. -SUPERCONDUCTORS WILL ALLOW US TO HAVE MORE USEABLE ELECTRICITY, WHILE LESS ELECTRICITY WILL BE LOST TO HEAT. -OHM’S LAW STATES THAT THE CURRENT IN A WIRE (I) IS EQUAL TO THE VOLTAGE (V) DIVIDED BY THE RESISTANCE (R). CURRENT = VOLTAGE RESISTANCE I=V R AMPERES = VOLTS OHMS -ELECTRONS MOVING THROUGH A WIRE CAN MOVE CONTINUOUSLY IN ONE DIRECTION OR THEY CAN CHANGE DIRECTION BACK AND FOURTH. -WHEN THEY FLOW IN THE SAME DIRECTION IT IS CALLED DIRECT CURRENT OR DC. BATTERIES ARE AN EXAMPLE OF DIRECT CURRENT. -WHEN THEY FLOW BACK AND FOURTH, REVERSING DIRECTION REGULARLY, IT IS CALLED ALTERNATING CURRENT OR AC. YOUR HOUSE OPERATES ON ALTERNATING CURRENT. AC IS BETTER FOR TRANSPORTING LARGE AMOUNTS OF ELECTRICITY. DO 1-3 SECTION REVIEW ON PAGE 30 #1-5 1-4 ELECTRIC CIRCUITS -AN ELECTRIC CIRCUIT PROVIDES A COMPLETE, CLOSED PATH FOR AN ELECTRIC CURRENT. -A CIRCUIT HAS DIFFERENT PARTS. IT HAS A SOURCE OF ENERGY, A LOAD, OR RESISTANCE, WIRES, AND A SWITCH. -THE SOURCE OF ENERGY CAN BE A BATTERY, THERMOCOUPLE, PHOTOCELL, OR EN ELECTRIC GENERATOR. -THE LOAD CAN BE A LIGHT BULB, APPLIANCE, MACHINE, OR A MOTOR. THE LOAD RESISTS THE FLOW OF ELECTRONS. THIS RESISTANCE IS CONVERTED TO LIGHT, HEAT, OR MECHANICAL ENERGY. -AN OPEN CIRCUIT IS WHEN THERE IS NOT A CONTINUOUS PATHWAY FOR THE ELECTRONS TO TRAVEL ALONG. EXAMPLE: WHEN THE LIGHTS ARE OFF, THE CIRCUIT IS OPEN = NO FLOW OF ELECTRONS = NO RESISTANCE = NO LIGHT. -A CLOSED CIRCUIT IS WHEN THERE IS A COMPLETE CONTINUOUS PATHWAY FOR THE ELECTRONS TO TRAVEL ALONG. EXAMPLE: WHEN THE LIGHTS ARE ON, THE CIRCUIT IS CLOSED = CONTINUOUS FLOW OF ELECTRONS = RESISTANCE = LIGHT. (SEE PICTURE ON P.31) -THERE ARE 2 TYPES OF ELECTRIC CIRCUITS DEPENDING ON HOW THE PARTS OF THE CIRCUIT ARE ARRANGED. -A SERIES CIRCUIT IS WHEN ALL THE PARTS OF AN ELECTRIC CIRCUIT ARE CONNECTED ONE AFTER ANOTHER. THERE IS ONLY 1 PATH THAT THE ELECTRONS CAN TAKE. IF THERE IS A BREAK IN ANY PART OF THE CIRCUIT, THEN ELECTRONS (CURRENT) CANNOT FLOW. -A PARALLEL CIRCUIT IS WHEN THERE IS MORE THEN 1 PATHWAY FOR THE ELECTRONS (CURRENT) TO TRAVEL. IF THERE IS A BREAK IN 1 PATHWAY, ELECTRONS CAN STILL MOVE THROUGH OTHER PATHWAYS. THESE TYPES OF CIRCUITS ARE USED IN HOUSES. -A SHORT CIRCUIT IS AN ACCIDENTAL CONNECTION THAT ALLOWS ELECTRONS (CURRENT) TO TAKE A SHORTER PATH AROUND A CIRCUIT. IF THE PATH IS SHORTER THEN THE CURRENT IS HIGHER BECAUSE THERE IS LESS RESISTANCE. -THE THIRD PRONG ON AN ELECTRICAL PLUG IS A GROUND WIRE. IT IS A SAFETY FEATURE THAT TRANSPORTS ANY ELECTRONS (CURRENT) THAT MAY BE CAUSING A SHORT CIRCUIT, INTO THE GROUND. -FUSES AND CIRCUIT BREAKERS ARE SAFETY FEATURES WITHIN A HOUSE THAT PREVENT EXTENSIVE DAMAGE. -IF TOO MANY THINGS ARE RUNNING ON THE SAME CIRCUIT, OR IF THE WIRES ARE OLD AND FRAYED, HEAT CAN BUILD UP. THIS HEAT CAN LEAD TO HOUSEHOLD FIRES. -FUSES PROTECT AGAINST TOO MUCH CURRENT FLOWING THROUGH AT ONE TIME. IF THE CURRENT IS TOO HIGH, THE METAL IN THE FUSE MELTS AND BREAKS THE FLOW OF ELECTRONS (CURRENT). ONCE A FUSE IS MELTED, IT MUST BE REPLACED. -CIRCUIT BREAKERS ARE SIMILAR TO FUSES IN THAT THEY PROTECT AGAINST A HIGH LEVEL OF CURRENT. THE DIFFERENCE IS THAT CIRCUIT BREAKERS HAVE A SWITCH THAT FLIPS ONCE THE CURRENT BECOMES TOO HIGH. IT DOES NOT MELT, SO IT DOES NOT HAVE TO BE REPLACED, JUST RESET. THIS METHOD IS MUCH EASIER THEN FUSES. DO 1-4 SECTION REVIEW ON PAGE 34 #1-4 1-5 ELECTRIC POWER -ELECTRIC POWER IS A MEASUER OF THE RATE AT WHICH ELECTRICITY DOES WORK OR PROVIDES ENERGY. POWER = VOLTAGE x CURRENT (P = V x I) OR WATTS = VOLTS x AMPERES -LIGHT BULBS OFTEN TELL YOU THE AMOUNT OF WATTS THAT THEY USE. FOR EXAMPLE: ELECTRICITY IN YOUR HOUSE IS 120V. THE LIGHTBULB OPERATES AT 0.5A. WHAT IS THE WATTAGE? -THE WATTAGE IS THE POWER OF THE BULB, OR THE RATE AT WHICH ENERGY IS DELIVERED. THE HIGHER THE WATTS = THE BRIGHTER THE BULB, AND THE MORE EXPENSIVE TO RUN. -TO MEASURE HIGH AMOUNTS OF POWER WE USE KILOWATTS (kW). REMEMBER, KILO = 1000. -OUR HOUSES RUN ON ELECTRIC ENERGY. WE GET OUR ENERGY FROM THE ELECTRIC COMPANY, WHICH MUST BE REGULATED AND THEN BILLED. AN ELECTRIC METER MEASURES THE AMOUNT OF ELECTRICITY WE USE PER MONTH. ENERGY = POWER x TIME OR E=Pxt -ELECTRIC ENERGY IS MEASURED IN KILOWATT-HOURS (kWh). KILOWATT-HOURS = KILOWATTS x HOURS -1 KILOWATT-HOUR IS EQUAL TO 1000 WATTS OF POWER USED FOR ONE HOUR OF TIME. COPY QUESTIONS 1. IF 1 KILOWATT-HOUR IS WORTH $0.08, HOW MUCH WOULD IT COST TO HAVE 3 100W BULBS FOR 4 HOURS? 2. IF 1 KILOWATT-HOUR IS WORTH $0.12, HOW MUCH WOULD IT COST TO HAVE A 1000W AIR CONDITIONER ON FOR 3 HOURS? -ELECTRIC SAFETY: 1. 2. 3. 4. 5. 6. NEVER USE ELECTRICITY CLOSE TO WATER. (CONDUCTOR) NEVER RUN WIRES UNDER CARPETS. (SHORT CIRCUIT) NEVER OVERLOAD A CIRCUIT. (SHORT CIRCUIT) ALWAYS REPAIR WORN OR FRAYED WIRES. (SHORT CIRCUIT) NEVER STICK YOUR FINGERS OR ANYTHING METAL INTO AN OUTLET. NEVER COME CLOSE TO WIRES ON POWER POLES OR TO FALLEN WIRES BECAUSE THEY OFTEN CARRY VERY HIGH CURRENTS WICH CAN BE FATAL. DO 1-5 SECTION REVIEW ON PAGE 38 #1-3 DO CHAPTER 1 REVIEW ON PAGE 42 #1-7 (M/C), #1-9 (T/F), #1-9 (C/M)