Engineering 10 Chp. 16 Units & Conversions Bruce Mayer, PE Licensed Electrical & Mechanical Engineer BMayer@Chabot. College. edu Engineering-10: Intro to Engineering 1 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Units Introduction § People measure quantities through comparisons with standards. § Every measured quantity has an associated “unit” Which is the name of the Standard. § Need to define sensible and practical "units" and "standards" that scientists & engineers everywhere can agree upon § Even though there exist an almost infinite number of different physical quantities, we need no more than a handful of “base” standards. Engineering-10: Intro to Engineering 2 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
SI System of Units § Système International d'Unités (International System of Units) § A Completely Consistent Set of Basic Units • Requires NO Conversion factors – e. g. , 18 inches = 1. 5 feet • Defined by UNCHANGING Physical Phenomena – Except for one. . . Engineering-10: Intro to Engineering 3 http: //www. bipm. org/en/si/ Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
SI System History § In 1960 The 11 th General Conference on Weights and Measures adopted the name SI System, for the recommended practical system of units of measurement. § The 1960 GCWM Specified Seven well-defined “Base” units which, by convention, are regarded as DIMENSIONALLY INDEPENDENT http: //www. bipm. org/en/si/ Engineering-10: Intro to Engineering 4 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
SI Base Units § From this List Observe SI Base Units Base quantity Name Symbol length meter m mass kilogram kg time second s electric current ampere A thermodynamic temperature kelvin K amount of substance mol candela cd luminous intensity § All But the kg are defined by Physical Phenomena • Examine the Defs Engineering-10: Intro to Engineering 5 • Very common Units – Mass (kg) – Length (m) – Time (s) • Some Not so Common Units – Current (A) – Temperature (K) • Some Uncommon Units – Substance amt (mol) – Luminous Int (cd) Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Meter Defined § Length or Distance (meter) § “The path traveled by light in vacuum during a time interval of 1/299792458 of a second. ” 1 meter Laser photon Engineering-10: Intro to Engineering 6 1/299792458 s Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Kilogram Defined § Mass (Kilogram) § a cylinder of PLATINUMIRIDIUM alloy maintained under vacuum conditions by the International Bureau of Weights and Measures in Paris If The Proto. Type Were Cubic, its Edge Length would be About 36. 2 mm (1. 42”); quite small Engineering-10: Intro to Engineering 7 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Second Defined § Time (Second) § The duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom • This is the Definition of an “Atomic” Clock – more than 200 atomic clocks are located in metrology institutes and observatories in more than 30 countries around the world Engineering-10: Intro to Engineering 8 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Amp Defined § Electric Current (ampere) § That constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 m apart in a vacuum, would produce between these conductors a force equal to 2 x 10− 7 Newton per metre of length. • What’s a Newton? → 1 kg-m/(s 2) Engineering-10: Intro to Engineering 9 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Kelvin (Temperature) Defined § § Thermodynamic temperature (Kelvin) The unit of thermodynamic temperature, is the fraction 1/273. 16 of thermodynamic temperature of the triple point of water. § 273. 16 K = 0. 0098 °C § Room Temperature (72 °F) is about 295. 5 Kelvins § NO “Degree” Sign Used with the Kelvin Unit Engineering-10: Intro to Engineering 10 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
mole (amt of Substance) Defined § Amount of § The mole is the amount of substance of a system which Substance contains as many elementary (mole) entities as there atoms in 0. 012 kilogram of carbon 12. § 1 mole = 6. 023 x 1023 entities • entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles. Engineering-10: Intro to Engineering 11 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Luminous Intensity Defined § The luminous intensity, in a given § Light direction, of a source that emits Brightness monochromatic radiation (one(candela) color light) of frequency 540 x 1012 Hertz and that has a radiant intensity in that direction of 1/683 watt per steradian § The are 4 (12. 57) Steradians in a sphere • 1 Str = 7. 96% of the Sphere Surface Engineering-10: Intro to Engineering 12 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Units Have Evolved § Candela Predecessor based on a Flame • Hence the Name § Temperature Based on Freezing points • Water • Platinum § Second Based on the Sidereal (standard) day Engineering-10: Intro to Engineering 13 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Units Have Evolved § History of the Meter (or Metre) • One ten millionth of the distance from the North pole to the equator. • The distance between two fine lines engraved near the ends of a platinum-iridium bar • 1 650 763. 73 wavelengths of a particular orange-red light emitted by atoms of krypton-86 (86 Kr). • The length of the path traveled by light in a vacuum during a time interval of 1/299 792 458 of a second. Engineering-10: Intro to Engineering 14 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
SI Derived Units § The Seven Base Units May be Arithmetically Combined to Produce “Derived Units” • e. g. : § Several Derived Units have Special Usefulness And are Given their OWN Names Engineering-10: Intro to Engineering 15 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Some Derived Units Derived quantity Name Symbol Expression in terms of other SI units Expression in terms of SI base units plane angle radian (a) rad - m·m-1 = 1 (b) solid angle steradian (a) sr (c) - m 2·m-2 = 1 (b) frequency hertz Hz - s-1 force newton N - m·kg·s-2 pressure, stress pascal Pa N/m 2 m-1·kg·s-2 energy, work, quantity of heat joule J N·m m 2·kg·s-2 power, radiant flux watt W J/s m 2·kg·s-3 electric charge, quantity of electricity coulomb C - s·A Engineering-10: Intro to Engineering 16 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Some (more) Derived Units Derived quantity Name Symbol Expression in terms of other SI units Expression in terms of SI base units electric potential difference, volt electromotive force V W/A m 2·kg·s-3·A-1 capacitance farad F C/V m-2·kg-1·s 4·A 2 electric resistance ohm V/A m 2·kg·s-3·A-2 electric conductance siemens S A/V m-2·kg-1·s 3·A 2 magnetic flux Weber Wb V·s m 2·kg·s-2·A-1 magnetic flux density tesla T Wb/m 2 kg·s-2·A-1 inductance henry H Wb/A m 2·kg·s-2·A-2 Celsius temperature degree Celsius °C - K luminous flux lumen lm cd·sr (c) m 2·m-2·cd = cd illuminance lux lx lm/m 2 Engineering-10: Intro to Engineering 17 m 2·m-4·cd = m 2·cd Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
SI prefixes – A form of Short. Hand Factor Name Symbol 1024 yotta 1021 Factor Name Symbol Y 10 -1 Deci d zetta Z 10 -2 Centi c 1018 exa E 10 -3 milli m 1015 peta P 10 -6 micro µ 1012 tera T 10 -9 nano n 109 giga G 10 -12 pico p 106 mega M 10 -15 femto f 103 kilo k 10 -18 atto a 102 hecto h 10 -21 zepto z 101 deka da 10 -24 yocto y Engineering-10: Intro to Engineering 18 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Derived Units Family Tree Engineering-10: Intro to Engineering 19 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Old (and Tired) Unit Sets § MKS • Stands for Meter-Kilogram-Second in the Most Common Units – Predecessor to The SI Units § CGS • Means Centimeter-Gram-Second – Still Widely Used § IPS, FPM, FPH • Inch-Pound-Sec, Foot-Lb-Min, Ft-Lb-Hour Engineering-10: Intro to Engineering 20 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
American Engineering System, AES – Still in (declining) Use Fundamental Dimension Base Unit So length foot (ft) mass pound (lbm) force pound (lbf) time second (sec) electric charge [Q] coulomb (C) absolute temperature degree Rankine (o. R) luminous intensity candela (cd) amount of substance mole (mol) Engineering-10: Intro to Engineering 21 m SA e A M re t E h SI e Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Conservation of Units § Principle of conservation of units: • Units on the LEFT side of an equation MUST be the SAME as those on the RIGHT side of an Equation § Then Have Dimensional Homogeneity • Needed to Prevent “Apples & Oranges” Confusion – e. g. , I Buy 100 ft of Wire at One Store and 50 m at another; how much total Wire do I have? (It’s NOT “ 150”) Engineering-10: Intro to Engineering 22 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Unit Conversion by Chain-Link § To Determine the Amount of Wire I have Need to Convert to Consistent (Homogeneous) Units § Start by Thinking About the Definition of “ 1” • Ref also Table 16. 8 in The Text • Now Consider a “minute” § Read as “ 60 Seconds per minute” Engineering-10: Intro to Engineering 23 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Chain-Link Unit Conversion § Units can also be Multiplied and Divided in a manner similar to Numbers • This how we get, say, “Square Feet” – e. g. ; Consider an 8 ft x 10 ft Engineer’s Cubicle in Dilbert-Land. How Much Work. Space Does the Engineer Have? § Now Back to the Wire • Want to Know how many FEET of Wire I have in Total Engineering-10: Intro to Engineering 24 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Chain-Link Unit Conversion cont. § Check in Table 16. 8 and Find “ 3. 2808 ft per meter” • Multiply the 50 m by this special Value of 1 § Can “Cancel” The Units by Division § So then the Total Wire = 264 ft Engineering-10: Intro to Engineering 25 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Chain Link Examples § A World-Class Sprinter can Run 100 m in 10 s. • How Fast is this in MPH? § Gasoline In Seoul Costs 1840 Korean-Won (W) for one Liter of Regular Unleaded • How Much is this in $ per Gallon – Find Currency Exchange Rate → $1 = 1150 W Engineering-10: Intro to Engineering 26 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Ton of Refrigeration § During his Presentation Mr. Ian Mc. Claren of South. Land Industries described the “Ice Storage” Cooling System Behind Bldg-1800. § He Noted that the Cooling Power of this system was Rated in “Tons” § What is a “Ton” of Cooling Power Engineering-10: Intro to Engineering 27 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Ton of Refrigeration § A TON of the refrigeration is defined, roughly, as the COOLING effect of melting 2000 lbs of water ICE over a 24 HOUR Period • From PHYS 4 C (or ASHRAE Hand. Book) find that the “Latent Heat of Fusion” for ice is 333. 55 k. J/kg § On Wht. Board Convert a Wht. Board “Ton of Refrigeration” to • k. W and Btu/hr Engineering-10: Intro to Engineering 28 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
White Board Examples § A 2003 Chevy z 06 corvette • Has a 5. 7 Liter V 8 Engine – What is the Engine Displacement in cubic-inches? • Develops 410 HP – What is the Power in Watts? § A Rheem Model #RAKA 060 JAZ Air Conditioner Costs $1432 and Has a Cooling Rating of 5 tons • What is the Cooling Rating in k. W? Engineering-10: Intro to Engineering 29 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
White Board Examples cont. § The USA FDA recommends that Adults consume 2200 Calories per Day • What then is the “Power Rating” of a Grown Human Being? – Note that there are TWO types of “Calories” 1. The Amount of Heat Required to Raise the Temperature of 1 GRAM of water by 1 °C (or 1 Kelvin) Ø Often Called the Gram-CAL; This is what is in the Text 2. The Amount of Heat Required to Raise the Temperature of 1 KILOgram of water by 1 °C Ø Often Called the Kg. CAL or Kilo. Cal; This is what you read on the side of Food Packaging Engineering-10: Intro to Engineering 30 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
All Done for Today How to Spend the Calories Engineering-10: Intro to Engineering 31 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
Engineering-10: Intro to Engineering 32 Bruce Mayer, PE BMayer@Chabot. College. edu • ENGR-10_Lec-16_Chp 16_Units-Conversions. ppt
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