Download 1-1 electric charge

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)