what is dc electricity. chapter 2. resistance the property of a material to inhibit the flow of...
TRANSCRIPT
What is DC Electricity.What is DC Electricity.
Chapter 2Chapter 2
ResistanceResistance
The property of a material to inhibit the flow of current.
ResistorResistor
ResistorResistor
Molded Carbon Composite
ResistorResistor
Wirewound
Film
Molded Carbon Composite
Wire woundWire wound
FilmFilm
Surface MountTechnology
SMT
ResistivityResistivity
AL
Resistivity: ExampleResistivity: ExampleA 1m long piece of gold has a cross
sectional area of 0.1cm2 . The resistivity of gold at 20°C is
2.24 X 10-8 ohm-meters.ρ
ρ =2.24 X 10-8 ohm-metersA = 0.1cm2 L = 1m
L = 1m
Resistivity: GoldResistivity: Goldρ =2.24 X 10-8 ohm-metersA = 0.1cm2 L = 1m
R =ρL A
R =(2.24 X 10-8 Ώ-m)(1m)
0.00001m2
R =0.00224 Ώ
Resistivity: CarbonResistivity: Carbonρ =50 X 10-5 ohm-metersA = 0.1cm2 L = 1m
R =ρL A
R =(50 X 10-5 Ώ-m)(1m)
0.00001m2
R =50 Ώ
Resistor Color CodeResistor Color Code
0
12
3
45
6
78
9
ToleranceTolerance
5%
The measure of how good a component is. How close it is to the
actual value.
10% 20%Gold Silver No Band
ToleranceTolerance
100100ΩΩ
5%: 95-1055%: 95-105ΩΩ
10%: 90-11010%: 90-110ΩΩ
20%: 80-12020%: 80-120ΩΩ
}Digits
36
Multiplier00000
Tolerance5 %
R =3600000 Ώ or 3.6M Ώ
}Digits
47
Multiplier
Tolerance20 %
R =36 Ώ
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
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
ExamplExampl
ee Battery: V = 1.5v, I = 1A
V=3vI= 3A
V=3v I=1A I=1A I=1A
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 = ER
Ohm’s LawOhm’s Law
RI
EFind: E
E = IxR
Ohm’s LawOhm’s Law
RI
EFind: R
R = E/I
Ohm’s LawOhm’s Law
RI
EFind: I
I = E/R
Ohm’s Law UnitsOhm’s Law Units
RΩIA
Ev
Ohm’s Law UnitsOhm’s Law Units
RkΩImA
E(v)
Ohm’s Law UnitsOhm’s Law Units
RMΩIμA
E(v)
Ohm’s Law ExampleOhm’s Law Example
RΩIA
Ev
R=2Ω, E=12vFind: I
I = E/R =12v/2Ω
I = 6A
Ohm’s Law ExampleOhm’s Law Example
RkΩImA
Ev
E=120, I=60mAFind: R
R = E/I =120v/60mA
R = 2kΩ
Ohm’s Law ExampleOhm’s Law Example
RkΩImA
Ev
R=10kΩ, I=12mAFind: E
E = IxR =12mAx10kΩ
I = 120v
Wheel of AnswersWheel of Answers
RΩIA
Ev
RkΩImA
Ev