Transcript current electricity

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
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
• Measured in
Amperes
– Amps or A
• Measured in Volts
– Volts or V
• Measured in Ohms
– ohms (W)
• Measures Amps
– measures current
• Voltmeter
• Measures Volts
– measure voltage
http://regentsprep.org/Regents/physics/phys03/bsimplcir/default.htm
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
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=W) relate
V = IR
• V : voltage of battery (e.g. 9 V battery)
• I : current (number of charges per second)
• R : resistance (e.g. light bulb, stereo, etc.)
POWER (again)
P=
2
I
R=
2
V/
R=IV
P : power (Watts)
I : current (Amps)
R : resistance (W)
V : voltage (Volts)
Remember: Power is energy per time (P=E/t)
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
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
http://www.regentsprep.org/Regents/physics/phys03/bparcir/default.htm
• 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
CH 22 HW
61. 18 Watts; 16200 J
64. 0.5 Amps; 9 Volts,
4.5 Watts; 1.6x104 J
65. 960 Watts
73. 120 Volts
79. 300 W; 60 W; 2
Amps
82. $513/kWh
92. 3 Amps; 12 Amps;
part b
58. 11.8 kW
23 HW
59. 404 CH
W
62. 37 W; 7.4 Volts; .88
Watts; 1.48 Watts
64. 26 W; 1.7 Amps; 37 &
7.7 Volts; 63 & 13 Watts
67. 10 W; 50 W; 19 Amps;
5.5 Amps; 2.2 Amps; 11
Amps
71. 230 W; 13 W; 3.6 Watts
73. 8.89 W;4.5 Amps; 2.5
Amps
81. 50 W; 0.5 Amps; 25 W
hot, 10 W cold
ELECTRICAL CIRCUITS
Pre-Class for Wednesday
4-25-12
What is Ohm’s Law?
• Start Chapter 23: Series and Parallel
Circuits
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
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
http://www.regentsprep.org/Regents/physics/phys03/bparcir/default.htm
• 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
OHM’S LAW
• Ohm defined how current(amps), voltage(volts),
and resistance(ohms=W) relate
V = IR
• V : voltage of battery (e.g. 9 V battery)
• I : current (number of charges per second)
• R : resistance (e.g. light bulb, stereo, etc.)
Pre-Class for Thursday
4-26-12
Power is measured in units called
_____.
a. Amperes
b. Watts
c. Kilowatt-hours
d. Joules
CH 22 HW
61. 18 Watts; 16200 J
64. 0.5 Amps; 9 Volts,
4.5 Watts; 1.6x104 J
65. 960 Watts
73. 120 Volts
79. 300 W; 60 W; 2
Amps
82. $513/kWh
92. 3 Amps; 12 Amps;
part b
58. 11.8 kW
59. 404 W CH 23 HW
62. 37 W; 7.4 Volts; .88
Watts; 1.48 Watts
64. 26 W; 1.7 Amps; 37 &
7.7 Volts; 63 & 13 Watts
67. 10 W; 50 W; 19 Amps;
5.5 Amps; 2.2 Amps; 11
Amps
71. 230 W; 13 W; 3.6 Watts
73. 8.89 W;4.5 Amps; 2.5
Amps
81. 50 W; 0.5 Amps; 25 W
hot, 10 W cold
CIRCUITS LAB
• MATERIALS:
–
–
–
–
Switches
Light bulbs
Batteries
Wires
• OBJECTIVE:
– Determine the difference between the
schematic and effects of series and
parallel circuits
• Connect the battery,
one bulb, a switch
PROCEDURES
together
• How bright is the
• Connect the
bulb?
battery, switch,
• Repeat for the other
and two bulbs in
bulb
parallel
• Connect the battery,
• How bright are
switch, and two bulbs
they?
in series
• How bright are the
bulbs?
SCHEMATICS
• Go back and draw a schematic for each setup (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