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CURRENT ELECTRICITY

CURRENT ELECTRICITY. CURRENT ELECTRICITY. THE STUDY OF CHARGES IN MOTION. KEY TOPICS. CIRCUITS CIRCUIT ELEMENTS CONDUCTORS/RESISTORS BATTERIES CIRCUIT PARAMETERS VOLTAGE/CURRENT /RESISTANCE SERIES AND PARALLEL CIRCUITS ELECTRICAL SHORTS ALTERNATING CURRENT. ELECTRICAL CIRCUIT.

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CURRENT ELECTRICITY

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  1. CURRENT ELECTRICITY

  2. CURRENT ELECTRICITY THE STUDY OF CHARGES IN MOTION

  3. KEY TOPICS • CIRCUITS • CIRCUIT ELEMENTS • CONDUCTORS/RESISTORS • BATTERIES • CIRCUIT PARAMETERS • VOLTAGE/CURRENT /RESISTANCE • SERIES AND PARALLEL CIRCUITS • ELECTRICAL SHORTS • ALTERNATING CURRENT

  4. ELECTRICAL CIRCUIT A COMPLETE PATH FOR ELECTRON FLOW

  5. ELECTRICAL CIRCUIT A CIRCUIT WILL CONSIST OF: SOURCES OF ELECTRICAL ENERGY BATTERIES, GENERATORS A COMPLETE CONDUCTING PATH PROVIDED BY WIRES DEVICES THAT CONVERT ELECTRICAL ENERGY TO OTHER FORMS LIGHTBULBS, RESISTORS, MOTORS, …

  6. ACTIVITY • GOOD CIRCUITS • ADDING BATTERIES • ADDING BATTERIES AND BULBS • MAKE A CIRCUIT WIRE

  7. PhET SIMULATION THE “CIRCUIT CONSTRUCTION KIT (DC ONLY)” CAN USE USED TO SHOW THE BASIC ELEMENTS IN AN ELECTRICAL CIRCUIT.

  8. BATTERIES 1.5 VOLTS -TERMINAL + TERMINAL STANDARD“D” CELL “AA” “AAA” “C” ARE LIKE THIS TOO

  9. CIRCUIT WIRE CONDUCTOR INSULATOR

  10. WHAT IS A CONDUCTOR? • A MATERIAL THAT ALLOWS FREE ELECTRON MOVEMENT • Examples: • Aluminum • Gold • Copper • All Metals

  11. WHAT IS AN INSULATOR? • A MATERIAL THAT DOES NOT CONDUCT ELECTRONS • EXAMPLES: • Plastics • Ceramics • Amber • VERY FEW OBJECTS ARE INSULATORS. • FOR SAFETY PURPOSES, ALWAYS ASSUME THAT AN UNKNOWN OBJECT IS A CONDUCTOR

  12. GOOD / POOR CONDUCTORS • MOST MATERIALS WILL CONDUCT ELECTRICITY. • IF AN OBJECT ALLOWS ELECTRONS TO EASILY PASS THROUGH, IT IS SAID TO BE A GOOD CONDUCTOR. • IF AN OBJECT DOES NOT ALLOW ELECTRONS TO EASILY PASS THROUGH, IT IS SAID TO BE A POOR CONDUCTOR. (USUALLY CALLED A RESISTOR)

  13. ACTIVITY • GOOD CONDUCTORS/POOR CONDUCTORS

  14. PhET SIMULATION THE “CIRCUIT CONSTRUCTION KIT (DC ONLY)” CAN USE USED TO TEST MATERIALS IN THE “GRAB BAG” TO SEE IF THEY ARE GOOD OR POOR CONDUCTORS.

  15. SWITCH • A CIRCUIT USED IN AN ELEMENTARY SCHOOL CLASSROOM SHOULD CONTAIN A SWITCH SO THAT ALL CONNECTIONS CAN BE MADE BEFORE ENERGY IS ALLOWED TO FLOW THROUGH THE CIRCUIT. • ALWAYS MAKE A “FLASH” CONNECTION BEFORE YOU ALLOW THE CURRENT TO FLOW CONTINUOUSLY.

  16. ACTIVITY • MAKE A SWITCH • PENCIL LEAD DIMMER SWITCH

  17. VOLTAGE • COMMON TERM FOR “POTENTIAL” • THE AMOUNT OF ENERGY PER ELECTRON PRODUCED BY AN ENERGY SOURCE (BATTERY)

  18. ELECTRICAL CURRENT THE RATE OF FLOW OF CHARGE

  19. ELECTRICAL CURRENT THE BRIGHTNESS OF A LIGHT BULB IS A GOOD INDICATOR OF THE RELATIVE AMOUNT OF CURRENT FLOWING THROUGH IT.

  20. 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.

  21. ELECTRICAL RESISTANCE RESISTANCE TO ELECTRON FLOW

  22. PhET SIMULATION THE PhET SIMULATION “BATTERY-RESISTOR CIRCUIT” CAN BE USED TO SHOW HOW RESISTANCE, VOLTAGE AND CURRENT ARE RELATED IN A CIRCUIT.

  23. Current, Voltage, Resistance • Current (I) • a measure of the rate of flow of electrons • measured in Amperes (A) • Voltage (V) • a measure of the energy per charge • measured in Volts (V) • Resistance (R) • a measure of the resistance to electron flow • measured in Ohms (W)

  24. OHM’S LAW IT IS MOST OFTEN WRITTEN AS V = I R OUR EXPERIMENTS DEMONSTRATE I = V / R THIS IS BECAUSE THE BRIGHTNESS OF THE BULBS INDICATES HOW “I” CHANGES AS WE CHANGE “V” AND “R”.

  25. PHET SIMULATION THE PhET SIMULATION CALLED “OHM’S LAW” CAN BE USED TO SHOW HOW CURRENT, VOLTAGE AND RESISTANCE ARE RELATED IN A SIMPLE CIRCUIT.

  26. SERIES CIRCUITS THE CURRENT HAS A SINGLE PATH AROUND THE CIRCUIT

  27. PhET SIMULATION THE “CIRCUIT CONSTRUCTION KIT (DC ONLY)” CAN BE USED TO SHOW A SERIES CIRCUIT.

  28. CIRCUIT ELEMENTS IN SERIES ALL HAVE THE SAME CURRENT THROUGH THEM

  29. ACTIVITY • SERIES CIRCUIT

  30. PARALLEL CIRCUIT THE CURRENT HAS MULTIPLE PATHS AROUND THE CIRCUIT

  31. PhET SIMULATION THE “CIRCUIT CONSTRUCTION KIT (DC ONLY)” CAN BE USED TO SHOW A PARALLEL CIRCUIT.

  32. CIRCUIT ELEMENTS IN PARALLEL ALL HAVE THE SAME VOLTAGE ACROSS THEM

  33. ACTIVITY • PARALLEL CIRCUIT

  34. BATTERIES IN SERIES THE TOTAL VOLTAGE PRODUCED BY BATTERIES IN SERIES IS THE SUM OF THE VOLTAGES OF ALL THE BATTERIES

  35. BATTERIES IN PARALLEL PRODUCE THE SAME VOLTAGE

  36. QUESTION HOW DO YOU CONNECT A BATTERY TO “JUMP START” YOUR CAR? WHY ARE BATTERIES CONNECTED IN BOTH PARALLEL AND SERIES IN SOME PORTABLE ELECTRICAL DEVICES?

  37. 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. ( A FIRE COULD RESULT)

  38. ACTIVITY • SHORT STUFF • OBSERVING A CIRCUIT WITH PHET

  39. 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.

  40. CIRCUIT BREAKER A MAGNETIC SWITCH THAT BREAKS THE CIRCUIT IF THE CURRENT IN THE CIRCUIT EXCEEDS ITS RATING

  41. ALTERNATING CURRENT (AC) • AN “AC” ENERGY SOURCE (USUALLY AN AC GENERATOR) PRODUCES A VOLTAGE THAT CONTINUOUSLY REVERSES POLARITY. • IN THE UNITED STATES, THE VOLTAGE DELIVERED TO A NORMAL HOUSEHOLD WALL OUTLET IS IN THE FORM OF A SINE WAVE WITH A MAXIMUM VOLTAGE OF 120 VOLTS AND A FREQUENCY OF 60 HERTZ. • THE RESULTING CURRENT (AC) WILL REVERSE 60 TIMES A SECOND.

  42. HOUSEHOLD AC VOLTAGE 120 V 120 V

  43. PhET SIMULATION • THE “CIRCUIT CONSTRUCTION KIT (AC+DC)” CAN USE USED TO SHOW HOW THE CURRENT REVERSES IN AN “AC” CIRCUIT. • AN “AC” VOLTAGE SOURCE MUST BE PLACED INTO THE CIRCUIT.

  44. SUMMARY • CIRCUITS • CIRCUIT ELEMENTS • CIRCUIT PARAMETERS • VOLTAGE/CURRENT /RESISTANCE • SERIES AND PARALLEL CIRCUITS • ELECTRICAL SHORTS • ALTERNATING CURRENT

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