1. CURRENT ELECTRICITY Pre-Class for Friday 4-24-09 Give one application of electricity. We will cover chapters 22 and 23, but the test will cover mostly 23

2. The Lazy Electron Electricity is like a lazy electron The electron sits on the couch watching TV eating chips and drinking a coke He doesn’t want to go anywhere When charge is to flow, like a river, the electron does not move, but he pushes his neighbor, who happens to be an a couch watching TV This process is repeated for the length of the wire

3. CURRENT The flow of positive charges (in theory) The flow of negative charges (in real life) A river of electrical energy that moves through a wire Must have a closed continuous loop to work

4. Current –number of charges that travel per second Battery –voltage (source) Resistance –impedes current –uses energy Ammeter –measures current Voltmeter –measure voltage Measured in Amperes –Amps or A Measured in Volts –Volts or V Measured in Ohms –ohms (  ) Measures Amps Measures Volts http://regentsprep.org/Regents/physics/phys03/bsimplcir/default.htm

5. SCHEMATICS A sketch of what the circuit looks like Represents how the current will flow in the circuit Specific types of symbols for sketches p. 597

7. Pre-Class for Tuesday 4-24-12 Draw the proper schematic symbols for: a battery, a resistor, and a switch.

8. OHM’S LAW Ohm defined how current(amps), voltage(volts), and resistance(ohms=  ) relate V = I R V : voltage of battery (e.g. 9 V battery) I : current (number of charges per second) R : resistance (e.g. light bulb, stereo, etc.)

10. POWER (again) P = I 2 R = V 2 / R = I V P : power (Watts) I : current (Amps) R : resistance (  ) V : voltage (Volts) Remember: Power is energy per time (P=E/t)

11. Practice Problems p594 #1-5  pick one p598 #6-8  pick one p600 #12 & 14 or #13 & 14  pick one or the other (2 problems) p603 #23-25  pick one Total of FIVE problems

12. CIRCUITS PARALLEL –current has multiple paths to follow –broken circuit may not stop electrical flow –voltage is the same through each resistor –current adds for each SERIES –current has only one path to follow –broken circuit stops all flow of electricity –current is the same through each resistor –voltage adds for each http://www.regentsprep.org/Regents/physics/phys03/bsercir/default.htmhttp://www.regentsprep.org/Regents/physics/phys03/bparcir/default.htm

13. 61. 18 Watts; 16200 J 64. 0.5 Amps; 9 Volts, 4.5 Watts; 1.6x10 4 J 65. 960 Watts 73. 120 Volts 79. 300  ; 60  ; 2 Amps 82. $513/kWh 92. 3 Amps; 12 Amps; part b 58. 11.8 k  59. 404  62. 37  7.4 Volts;.88 Watts; 1.48 Watts 64. 26  ; 1.7 Amps; 37 & 7.7 Volts; 63 & 13 Watts 67. 10  ; 50  ; 19 Amps; 5.5 Amps; 2.2 Amps; 11 Amps 71. 230  ; 13  ; 3.6 Watts 73. 8.89  ;4.5 Amps; 2.5 Amps 81. 50  ; 0.5 Amps; 25  hot, 10  cold CH 22 HW CH 23 HW

14. ELECTRICAL CIRCUITS Pre-Class for Wednesday 4-25-12 What is Ohm’s Law? Start Chapter 23: Series and Parallel Circuits

15. SCHEMATICS A sketch of what the circuit looks like Represents how the current will flow in the circuit Specific types of symbols for sketches p. 597

16. CIRCUITS PARALLEL –current has multiple paths to follow –broken circuit may not stop electrical flow –voltage is the same through each resistor –current adds for each SERIES –current has only one path to follow –broken circuit stops all flow of electricity –current is the same through each resistor –voltage adds for each http://www.regentsprep.org/Regents/physics/phys03/bsercir/default.htmhttp://www.regentsprep.org/Regents/physics/phys03/bparcir/default.htm

17. Ohm defined how current(amps), voltage(volts), and resistance(ohms=  ) relate V = I R V : voltage of battery (e.g. 9 V battery) I : current (number of charges per second) R : resistance (e.g. light bulb, stereo, etc.) OHM’S OHM’S LAW

23. Pre-Class for Thursday 4-26-12 Power is measured in units called _____. a.Amperes b.Watts c.Kilowatt-hours d.Joules

24. 61. 18 Watts; 16200 J 64. 0.5 Amps; 9 Volts, 4.5 Watts; 1.6x10 4 J 65. 960 Watts 73. 120 Volts 79. 300  ; 60  ; 2 Amps 82. $513/kWh 92. 3 Amps; 12 Amps; part b 58. 11.8 k  59. 404  62. 37  7.4 Volts;.88 Watts; 1.48 Watts 64. 26  ; 1.7 Amps; 37 & 7.7 Volts; 63 & 13 Watts 67. 10  ; 50  ; 19 Amps; 5.5 Amps; 2.2 Amps; 11 Amps 71. 230  ; 13  ; 3.6 Watts 73. 8.89  ;4.5 Amps; 2.5 Amps 81. 50  ; 0.5 Amps; 25  hot, 10  cold CH 22 HW CH 23 HW

25. CIRCUITS LAB MATERIALS: –Switches –Light bulbs –Batteries –Wires OBJECTIVE: –Determine the difference between the schematic and effects of series and parallel circuits

26. PROCEDURES Connect the battery, one bulb, a switch together How bright is the bulb? Repeat for the other bulb Connect the battery, switch, and two bulbs in series How bright are the bulbs? Connect the battery, switch, and two bulbs in parallel How bright are they?

27. SCHEMATICS Go back and draw a schematic for each set- up (4 drawings) Remember that a schematic is not how it looks to us, but what the current sees It is just to help us understand where the current is going Be sure to use the proper symbols