Transcript Slide 1
STATIC ELECTRICITY THE STUDY OF CHARGES AT REST ACTIVITY MODEL OF AN ATOM CHARGE A BALLOON STATIC ELECTRICITY When you rub a balloon on your hair you scrape electrons off the atoms of your hair onto the balloon. The atoms of the balloon apparently have more “grab” on electrons. “Laws of Attraction” Opposite Charges Attract + - Like Charges Repel + + ACTIVITY STYROFOAM ELECTROSCOPE A COULOMB THE FUNDAMENTAL UNIT OF CHARGE IT IS EQUAL TO THE CHARGE OF 6.25 BILLION BILLION ELECTRONS COULOMBS LAW ELECTRICAL FORCE DEPENDS ON THE SIZE OF THE CHARGES AND THE DISTANCE BETWEEN THE CHARGES Coulomb’s Law The force between charges varies inversely with the square of their separation distances. + + + + COULOMB’S LAW F = k X Q1 X Q2 / 2 D ACTIVITY POLARIZING A STICK Polarization Polarized objects have an uneven distribution of charge. A polarized object has no net charge. - - - - - - - - - - - - - - - - - - - - - Meter Stick + + + + + + + + + + + + + + + + + + + + Weak Force + - + + + + + + + - - - - - - - - + + + + + + + + Strong Force - - - - - - - + + + + CURRENT ELECTRICITY THE STUDY OF CHARGES IN MOTION ELECTRICAL CIRCUIT A COMPLETE PATH FOR ELECTRON FLOW ACTIVITY ELECTICAL ALTERNATIVES XMAS TREE BULB MAKE A WIRE CIRCUIT WIRE CONDUCTOR INSULATOR ELECTRICAL CIRCUIT CONSISTS OF •SOURCES OF ELECTRICAL ENERGY •A COMPLETE CONDUCTING PATH •DEVICES THAT CONVERT ELECTRICAL ENERGY TO OTHER FORMS ACTIVITY ADDING BATTERIES MAKE A SWITCH What is a conductor? a material that allows free electron movement Examples: Aluminum Gold Copper All Metals ACTIVITY GOOD CONDUCTORS POOR CONDUCTORS What is an insulator? a material that does not allow electrons to flow freely Examples: Plastics Ceramics Amber ACTIVITY CONDUCTIVITY TESTER LIGHT BULB FILAMENT CONDUCTOR ACTIVITY CREATING LIGHT BATTERIES - TERMINAL 1.5 VOLTS + TERMINAL STANDARD “D” CELL VOLTAGE COMMON TERM FOR “POTENTIAL” THE AMOUNT OF ENERGY PER ELECTRON PRODUCED BY AN ENERGY SOURCE (BATTERY) ELECTRICAL CURRENT THE RATE OF FLOW OF CHARGE ELECTRICAL CURRENT THE BRIGHTNESS OF A LIGHT BULB IS A GOOD INDICATOR OF THE RELATIVE AMOUNT OF CURRENT FLOWING THROUGH IT. ELECTRICAL CURRENT ELECTRONS FLOW OUT OF THE NEGATIVE TERMINAL OF A BATTERY. AFTER ELECTRONS TRAVEL THROUGH THE CIRCUIT, THEY FLOW INTO THE POSITIVE TERMINAL OF THE BATTERY. ELECTRICAL RESISTANCE RESISTANCE TO ELECTRON FLOW ACTIVITY PENCIL LEAD DIMMER SWITCH LIGHT DIMMER ELECTRICAL SHORT A LOW RESISTANCE PATH ACROSS THE TERMINALS OF AN ELECTRICAL CIRCUIT ELEMENT. IF IT OCCURS ACROSS A BATTERY, GENERATOR OR ANY ENERGY SOURCE, IT CAN CAUSE TOO HIGH OF A CURRENT. ELECTRICAL SHORT SOMETIMES A RESISTOR CAN HAVE A SHORT ACROSS ITS LEADS. IF THIS OCCURS AND ANOTHER RESISTOR IS IN THE CIRCUIT, THE OTHER RESISTOR MAY POSSESS ENOUGH RESISTANCE TO KEEP THE CURRENT FROM BECOMING TOO LARGE. WHEN THIS OCCURS, NO CURRENT WILL PASS THROUGH THE SHORTED RESISTOR. CIRCUIT DIAGRAM A CONCISE REPRESENTATION OF AN ELECTRICAL CIRCUIT UTILIZING STANDARD ELECTRICAL SYMBOLS. IT SHOULD BE ACCURATE, SIMPLE AND NEAT. ACTIVITY ELECTROSQUARES DRAWING CIRCUITS ELECTRON CURRENT A MEASURE OF THE RATE OF FLOW OF ELECTRON CHARGE THROUGH A CIRCUIT. THE DIRECTION OF FLOW IS FROM THE NEGATIVE SIDE OF THE ENERGY SOURCE THROUGH THE CIRCUIT TO THE POSITIVE SIDE OF THE ENERGY SOURCE. OHM’S LAW THE CURRENT THROUGH A RESISTOR IS PROPORTIONAL TO THE APPLIED VOLTAGE AND INVERSELY PROPORTIONAL TO ITS RESISTANCE. I=V/R I = CURRENT V = VOLTAGE R = RESISTANCE ELECTRICAL CURRENT • A MEASURE OF THE NUMBER OF COULOMBS PER SECOND THAT PASSES A POINT IN A CIRCUIT. • THE UNIT OF CURRENT IS THE AMPERE = COULOMB PER SECOND VOLTAGE (POTENTIAL) THE ENERGY PER CHARGE LOST OR GAINED BY CHARGES AS THEY PASS THROUGH A DEVICE. THE UNIT IS THE VOLT = JOULE PER COULOMB RESISTANCE A MEASURE OF THE RESISTANCE TO ELECTRON FLOW. THE UNIT IS THE OHM = VOLT PER AMPERE SYMBOL FOR OHM IS W RESISTANCE RESISTANCE CAN BE RELATED TO THE AMOUNT OF VOLTAGE NEEDED TO PRODUCE A AMPERE OF CURRENT. IF IT TAKES TWO VOLTS TO PRODUCE ONE AMPERE, THE RESISTANCE IS TWO OHMS Current, Voltage, Resistance Current a measure of the rate of flow of electrons measures in Amperes (A) Voltage a measure of the energy per charge measured in Volts (V) Resistance a measure of the resistance to electron flow measured in Ohms (W) SERIES CIRCUITS THE CURRENT HAS A SINGLE PATH AROUND THE CIRCUIT ACTIVITY SERIES CIRCUIT CIRCUIT ELEMENTS IN SERIES ALL HAVE THE SAME CURRENT THROUGH THEM PARALLEL CIRCUIT THE CURRENT HAS MULTIPLE PATHS AROUND THE CIRCUIT ACTIVITY PARALLEL CIRCUITS CIRCUIT ELEMENTS IN PARALLEL ALL HAVE THE SAME VOLTAGE ACROSS THEM RESISTORS IN SERIES THE TOTAL RESISTANCE IS THE SUM OF ALL RESISTORS IN SERIES. RESISTORS IN PARALLEL THIS COMBINATION POSSESSES LESS COMBINED RESISTANCE THAN THE LOWEST RESISTOR IN THE COMBINATION. BATTERIES IN SERIES THE TOTAL VOLTAGE PRODUCED BY BATTERIES IN SERIES IS THE SUM OF THE VOLTAGES OF EACH BATTERY BATTERIES IN PARALLEL PRODUCE THE SAME VOLTAGE QUESTION HOW DO YOU CONNECT A BATTERY TO “JUMP START” YOU CAR? WHY ARE BATTERIES CONNECTED IN BOTH PARALLEL AND SERIES IN SOME PORTABLE DEVICES? ACTIVITY ELECTRIC CIRCUITS DIODE DIODE MEANS TO CONDUCT IN ONLY ONE DIRECTION WILL CONDUCT ELECTRONS WILL NOT CONDUCT ELECTRONS LIGHT EMITTING DIODE (LED) A DIODE THAT EMITS LIGHT WHEN CURRENT IS PRESENT. MOST LED’S REQUIRE ONLY A MILLIAMP TO BE SEEN. FUSE A FUSE IS PLACED IN SERIES WITH THE ENERGY SOURCE. IT IS RATED TO BURN (OR MELT) IF THE CURRENT THROUGH IT EXCEEDS ITS RATING. ACTIVITY CIRCUIT BREAKERS CIRCUIT BREAKER A MAGNETIC SWITCH THAT BREAKS THE CIRCUIT IF THE CURRENT IN THE CIRCUIT EXCEEDS ITS RATING SWITCHES SINGLE POLE SINGLE THROW SINGLE POLE DOUBLE THROW ACTIVITY MAKE A SWITCH LEMON BATTERY THE ZINC TERMINAL IS NEGATIVE THE COPPER TERMINAL IS POSITIVE ABOUT 1 VOLT IS PRODUCED BY A SINGLE LEMON BATTERY YOU NEED TWO LEMONS TO LIGHT AN LED ACTIVITY LIGHT AN LED USING LEMON BATTERIES