CURRENT ELECTRICITY

• Pre-Class for Friday 4-24-09Give one

application of electricity.

• We will cover chapters 22 and 23, but the test will cover mostly 23

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

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

• 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

SCHEMATICSSCHEMATICS

• 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

Pre-Class for Tuesday 4-24-12

Draw the proper schematic symbols for: a battery, a resistor, and a switch.

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.)

POWERPOWER ( (againagain))

P = I2 R = V2/ R = I VP : power (Watts)

I : current (Amps)

R : resistance ()

V : voltage (Volts)

Remember: Power is energy per time (P=E/t)

Practice ProblemsPractice 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 problemsTotal of FIVE problems

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.htm http://www.regentsprep.org/Regents/physics/phys03/bparcir/default.htm

61. 18 Watts; 16200 J64. 0.5 Amps; 9 Volts,

4.5 Watts; 1.6x104 J65. 960 Watts73. 120 Volts79. 300 ; 60 ; 2

Amps82. $513/kWh92. 3 Amps; 12 Amps;

part b

58. 11.8 k59. 404 62. 37 7.4 Volts; .88

Watts; 1.48 Watts64. 26 ; 1.7 Amps; 37 &

7.7 Volts; 63 & 13 Watts67. 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 HWCH 22 HW CH 23 HWCH 23 HW

ELECTRICAL CIRCUITSELECTRICAL CIRCUITS

Pre-Class for Pre-Class for Wednesday Wednesday

4-25-124-25-12

What is Ohm’s Law?

• Start Chapter 23: Series and Parallel Circuits

SCHEMATICSSCHEMATICS

• 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

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.htm http://www.regentsprep.org/Regents/physics/phys03/bparcir/default.htm

• 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’SOHM’S LAW

Pre-Class for Thursday 4-26-12

Power is measured in units called _____.

a. Amperesb. Wattsc. Kilowatt-hoursd. Joules

61. 18 Watts; 16200 J64. 0.5 Amps; 9 Volts,

4.5 Watts; 1.6x104 J65. 960 Watts73. 120 Volts79. 300 ; 60 ; 2

Amps82. $513/kWh92. 3 Amps; 12 Amps;

part b

58. 11.8 k59. 404 62. 37 7.4 Volts; .88

Watts; 1.48 Watts64. 26 ; 1.7 Amps; 37 &

7.7 Volts; 63 & 13 Watts67. 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 HWCH 22 HW CH 23 HWCH 23 HW

CIRCUITS LAB

• MATERIALS:– Switches– Light bulbs– Batteries– Wires

• OBJECTIVE:– Determine the difference between the

schematic and effects of series and parallel circuits

PROCEDURESPROCEDURES• 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?

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