VoltageVoltage
Chapter 3Chapter 3
Voltage (V or E)Voltage (V or E)
Supplies the force or pressure required to move electrons
through a circuit.
Unit – Volt (V)
AKA – Electromotive Force EMF
Voltage SourcesVoltage Sources
Friction – Van de Graaf Generator
Voltage SourceVoltage Source
Generator – Most Common
Voltage SourceVoltage Source
Cell – Battery: Chemical Reaction
Voltage SourceVoltage Source
Photovoltaic CellLight → Voltage
Voltage SourceVoltage Source
ThermocoupleHeat → Voltage
Voltage SourceVoltage Source
Piezoelectric EffectPressure → Voltage
Cells and BatteriesCells and Batteries
Primary CellsCannot be Recharged
Cells and BatteriesCells and Batteries
Secondary CellsCan be Recharged
Connecting Voltage SourcesConnecting Voltage Sources
Series Aiding Series Opposing
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Voltage SourcesVoltage SourcesVoltage sources added in Series
increase the Voltage and the Current stays the same.
V = 1.5v I = 1A
V = 4.5v I = 1A
V = 4.5v I = 1A
Voltage SourcesVoltage SourcesVoltage sources added in Parallel
increase the Current and the Voltage stays the same.
V = 1.5v I = 1A
V = 1.5v I = 3A
V=1.5v I =3A
ExampleExample Battery: V = 1.5v, I = 1A
V=3vI= 3A
V=3v I=1A I=1A I=1A
V=3v I=3A
Battery: V = 1.5v and I = 100mA
9v100mA 100mA 100mA 100mA 100mA
VT = 9vIT =500mA
VT = 9v and IT = 500ma
VT = 9vIT =500mA
Voltage RiseVoltage Rise
Voltage Rise can be defined as the energy added to a circuit.
Voltage DropVoltage Drop
A Voltage Drop is defined as the energy removed or used in a circuit.
Voltage DropVoltage Drop
Earth GroundEarth GroundZero Voltage reference point.Limits build up of electrical charge.Limits exposure to high voltages.
Electrical GroundElectrical Ground
Ground is defined as the zero reference point which against
all voltages are measured.
Electrical Ground in a CarElectrical Ground in a Car
Jumping a CarJumping a Car
BadBattery
Ohm’s LawOhm’s LawThe Current(I) in a circuit is directly
proportional to the Voltage(E,V) and inversely proportional to the
Resistance(R).
I = VR
Ohm’s LawOhm’s Law
RI
VFind: V
V = IxR
Ohm’s LawOhm’s Law
RI
VFind: R
R = V/I
Ohm’s LawOhm’s Law
RI
VFind: I
I = V/R
Ohm’s Law UnitsOhm’s Law Units
RΩIA
Vv
Ohm’s Law UnitsOhm’s Law Units
RkΩImA
V(v)
Ohm’s Law ExampleOhm’s Law Example
RΩIA
Vv
R=2Ω, V=12vFind: I
I = V/R =12v/2Ω
I = 6A
Ohm’s Law ExampleOhm’s Law Example
RkΩImA
Vv
V=120, I=60mAFind: R
R = V/I =120v/60mA
R = 2kΩ
Ohm’s Law ExampleOhm’s Law Example
RkΩImA
Vv
R=10kΩ, I=12mAFind: V
V = IxR =12mAx10kΩ
V = 120v
Wheel of AnswersWheel of Answers
RΩIA
Vv
RkΩImA
Vv
PowerPowerPower is how fast work is done.
Work is done when force causes motion.
Electric Force: Voltage
Moving: Electrons
PowerPowerPower: P
Unit for Power: WattWatt: W
P = IV
Power LawPower Law
VI
PFind: P
P = IxV
Power LawPower Law
VI
PFind: V
V = P/I
Power LawPower Law
VI
PFind: I
I = P/V
Power Law UnitsPower Law Units
VVIA
PW
Power Law UnitsPower Law Units
VVImA
PmW
How much power does a 12V computer fan use if it is drawing 1.5A?
V = 12VI = 1.5A
P=IV
P=(1.5A)(12V)
P = (18W)
Combining Ohm’s and Power LawsCombining Ohm’s and Power Laws
RIVP = I2R
V2
RP =
Classwork Classwork Read the following Chapters:Read the following Chapters:
»Chapter 2: AllChapter 2: All
»Chapter 3: AllChapter 3: All
»Chapter 4: Pages 32-44Chapter 4: Pages 32-44
»Chapter 5: Pages 49-52Chapter 5: Pages 49-52
Answer the questions after each section:Answer the questions after each section:Write down question and answer!!!Write down question and answer!!!
• Perform Self-Test at the end of the chapter Perform Self-Test at the end of the chapter Write down question and answer!!!Write down question and answer!!!