Learning with PurposeSlide 1
Learning with PurposeSlide 1
Chapter 1: Quantities and Units
Instructor: Jean-François MILLITHALER
http://faculty.uml.edu/JeanFrancois_Millithaler/FunElec/Spring2017
Learning with PurposeSlide 2
10x
Power of Ten
Base Exponent
104 = 1 x 104 = 10000 = 10,000
0.00000000000000000016 = 1.6 x 10-19
Learning with PurposeSlide 3
Convenient method for expressing large and small numbers
Examples:
23,000,000 = 2.3 x 107 (Scientific Notation)= 23 x 106 (Engineering Notation)
0.0000000055 = 5.5 x 10-9 (Scientific Notation)= 55 x 10-10 (Engineering Notation)
Use EE Key on your calculator
Scientific and Engineering Notation
Learning with PurposeSlide 4
Interesting point: Water
1x10-3 L (1 mL) = 1 cm-3 = 1 g
Requires 1 cal of energy to heat up of 1 K
Corresponds to 1% between freezing and boiling point
International System SI
Quantity Unit Symbol
Length Meter m
Mass Kilogram kg
Time Second s
Electric current Ampere A
Temperature Kelvin K
Learning with PurposeSlide 5
Metric and Imperial Systems
Examples
FAHRENHEIT CELCIUS KELVIN
212 100 373.15 Water boils
98.6 37 310 Human body temperature
68 20 300 Room temperature
32 0 273.15 Water freezing
-320 -195 77 Liquide Nitrogen temperature
-459.67 -273.15 0 Absolute zero
Learning with PurposeSlide 6
Units are based on fundamental units from the MKS system
Meter-Kilogram-Second
Important Electrical Units
Quantity Unit Symbol
Current Ampere A
Charge Coulomb C
Voltage Volt V
Resistance Ohm W
Power Watt Watt
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P
T
G
M
k
Engineering Metric Prefixes
m
m
n
p
f
Peta
Tera
Giga
Mega
kilo
milli
micro
nano
pico
femto
1015
1013
109
106
103
10-3
10-6
10-9
10-12
10-15
Learning with PurposeSlide 8
Convert 0.03 MV to kilovolts (kV)
• 0.03 MV = 0.03 x 106 V = 3 x 10-2 x 103 x 103 V = 30 kV
Convert 470,000 pA to milliamperes (mA).
• 4.7 x 105 x 10-12 A = 4.7 x 10-4 x 10-3 A = 4.7 x 10-4 mA
Add 0.06 MW and 95 kW and express the result in kW.
• 6 x 10-2 x 106 + 95 x 103 = 6 x 104 + 9.5 x 104 = 15.5 x 104 W
• = 155 kW = 0.155 MW
Add 50 mV and 25,000 mV and express the result in mV.
• 50 x 10-3 + 25 x 103 x 10-6 = (50 + 25) x10-3 V = 75 mV
Metric Conversion
Examples
kV3 x 10-2+3
Learning with PurposeSlide 9
Error is the difference between the true or best accepted value and the measured value
Accuracy is an indication of the range of error in a measurement
Precision is a measure of repeatability
Error, Accuracy, and Precision
Physicist Tv
Learning with PurposeSlide 10
When reporting a measured value, one uncertain digit may be retained but other uncertain digits should be discarded. Normally this is the same number of digits as in the original measurement.
Example
• 1.0 divided by 3.0 = 0.333333
• 1.0 and 3.0 have 2 significant digits
• Result with same uncertainty = 0.3
Significant Digits
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Rules for determining if a reported digit is significant are: • Nonzero digits are always considered to be significant.
• Ex: 543.26
• Zeros to the left of the first nonzero digit are never significant.
• Ex: 0.000548
• Zeros between nonzero digits are always significant.
• Ex: 6904.903
• Zeros to the right of the decimal point for a decimal number are significant.
• Ex: 8.00
• Zeros to the left of the decimal point with a whole number may or may not be significant depending on the measurement.
• Ex: 4000 does not have a clear number of significant digits
Significant Digits
Learning with PurposeSlide 12
Rounding is the process of discarding meaningless digits. Rules for rounding are:
• If the digit dropped is greater than 5, increase the last retained digit by 1
• If the digit dropped is less than 5, do not change the last retained digit.
• If the digit dropped is 5, increase the last retained digit if it makes it even, otherwise do not. This is called the "round-to-even" rule.
Rounding numbers
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Outlet: 120 V in USA, 220 V in Europe
Circuits protected with Ground-Fault Circuit Interrupter (GFCI)
Utility voltages
Safety
Neutral Hot
Ground
Reset
Test
Learning with PurposeSlide 14
Safety is always a concern with electrical circuits. Knowing the rules and maintaining a safe environment is everyone’s job.
A few important safety suggestions are:
• Do not work alone, or when you are drowsy.
• Do not wear conductive jewelry.
• Know the potential hazards of the equipment you are working on; check equipment and power cords frequently.
• Avoid all contact with energized circuits; even low voltage circuits.
• Maintain a clean workspace.
• Know the location of power shutoff and fire extinguishers.
• Don’t have food or drinks in the laboratory or work area.
Electrical Safety