Transcript What is DC Electricity.

What is DC Electricity.
Chapter 2
Resistance
The property of a material to
inhibit the flow of current.
Resistor
Resistor
Molded Carbon Composite
Resistor
Film
Molded
Carbon
Composite
Wirewound
Wire wound
Film
Surface
Mount
Technology
SMT
Resistivity
A
Resistivity: Example
A 1m long piece of gold has a cross
2
sectional area of 0.1cm . The
resistivity of gold at 20°C is
2.24 X 10-8 ohm-meters.ρ
-8
10
ρ =2.24 X
2
A = 0.1cm
L = 1m
ohm-meters
L = 1m
Resistivity: Gold
ρ =2.24 X 10-8 ohm-meters
2
L = 1m
A = 0.1cm
ρL
R=
A
R=
(2.24 X 10-8 Ώ-m)(1m)
2
0.00001m
R =0.00224 Ώ
Resistivity: Carbon
ρ =50 X 10-5 ohm-meters
2
L = 1m
A = 0.1cm
ρL
R=
A
R=
(50 X 10-5 Ώ-m)(1m)
R =50 Ώ
2
0.00001m
Resistor Color Code
0
1
2
3
4
5
6
7
8
9
Tolerance
The measure of how good a
component is. How close it is to the
actual value.
5%
10%
20%
Gold
Silver
No Band
Tolerance
5%: 95-105Ω
100Ω
10%: 90-110Ω
20%: 80-120Ω
}
Digits
36
Multiplier
00000
Tolerance
5%
R =3600000 Ώ or 3.6M Ώ
}
Digits
47
Multiplier
R =36 Ώ
Tolerance
20 %
Voltage Sources
Voltage sources added in Series
increase the Voltage and the Current
stays the same.
V = 1.5v
I = 1A
V = 4.5v
I = 1A
Voltage Sources
Voltage sources added in Parallel
increase the Current and the Voltage
stays the same.
V = 1.5v
I = 1A
V = 1.5v
I = 3A
Battery: V = 1.5v, I = 1A
V=3v I=1A I=1A I=1A
Exampl
e
V=3v
I= 3A
Ohm’s Law
The Current(I) in a circuit is directly
proportional to the Voltage(E,V) and
inversely proportional to the
Resistance(R).
E
I=
R
Ohm’s Law
E
I R
Find: E
E=
x
IR
Ohm’s Law
E
I R
Find: R
R = E/I
Ohm’s Law
E
I R
Find: I
I = E/R
Ohm’s Law Units
Ev
IA RΩ
Ohm’s Law Units
E(v)
ImA RkΩ
Ohm’s Law Units
E(v)
IμA RMΩ
Ohm’s Law Example
Ev
IA RΩ
R=2Ω, E=12v
Find: I
I = E/R
=12v/2Ω
I = 6A
Ohm’s Law Example
Ev
E=120, I=60mA
Find: R
R = E/I
ImA RkΩ
=120v/60mA
R = 2kΩ
Ohm’s Law Example
Ev
R=10kΩ, I=12mA
Find: E
E = IxR
ImA RkΩ
=12mAx10kΩ
I = 120v
Wheel of Answers
Ev
IA RΩ
Ev
ImA RkΩ