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Chapter 2

Chapter 2. Prefixes, Units and Unit Conversion. Quick review on exponents. 10 3 = 10x10x10 = 1000  10 x 3 3 x 10 3 = 3x10x10x10 = 3000 2 4 = 2x2x2x2=16 10 6 = 10x10x10x10x10x10 = 1,000,000 10 -3 = 1/(10 3 ) = 1/1000 = .001 10 -6 = 1/(10 6 ) = 1/1000,000 = .000001

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Chapter 2

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  1. Chapter 2 Prefixes, Units and Unit Conversion

  2. Quick review on exponents • 103 = 10x10x10 = 1000  10 x 3 • 3 x 103 = 3x10x10x10 = 3000 • 24 = 2x2x2x2=16 • 106 = 10x10x10x10x10x10 = 1,000,000 • 10-3 = 1/(103) = 1/1000 = .001 • 10-6 = 1/(106) = 1/1000,000 = .000001 • 5 x 10-6 = 5 x 1/(106) = 5x.000001 = .000005

  3. Scientific Units Parameter Unit • Length • Mass • Time For Electronics • Voltage • Current • Resistance Meter [m] Kilogram [kg] Second [s] Volt [V] Amp [A] Ohm [Ω]

  4. Other Units

  5. Prefixes • How many meters are there in a kilometer? • 1000 • How many milliseconds are there in a second? • 1000 • How many bytes are there in a Gigabyte? • 1,000,000,000

  6. Prefixes (cont.) • Kilo, milli, and Giga are all called prefixes. • Can you guess why they call them prefixes? • Because they come before the unit such as millisecond. • Prefixes are used to represent how much of the particular unit is being represented

  7. Prefixes we’ll use in Elec50A

  8. In your book they show other prefixes we won’t use much if at all.

  9. Quick Prefix Quiz • How seconds are there in a Gs? • 1 billion • How many volts in a mV? • .001 • How many mV in a volt? • 1000 • How many amps in a kiloAmp (kA)? • 1000

  10. Quick Prefix Quiz (cont.) • How small is a nA • 1 billionth or .000000001 A or 10-9 • How small is a uΩ? • 1 millionth or .000001Ω or 10-6 • How big is a pV? • 1 trillionth of a volt or 10-12 V

  11. 3 ways to write a number Regular Way Using Prefixes Scientific Notation 1 million volts 1 thousandth of an amp 1 millionth of an ohm 1 billion grams 5 thousand meters 1 second 1,000,000 V .001 A .000001 Ω 1,000,000,000 g 5000 m 1 s 1MV 1mA 1uΩ 1Gg 5km 1s 1x106 V 1x10-3 A 1x10-6 Ω 1x109 g 5x103 m 1x100 s Notice that the prefixes take place of the scientific notation and everything else stays the same. Meaning – k = x103

  12. Write the following in scientific notation: • 3mV • 18kV • 43ms • 2.1GA • 30uA • 57ps 3x10-3V 18x103V 43x10-3s 2.1x109A 30x10-6A 57x10-12s

  13. Write the following using prefixes Notice “m” replaced all of “x10-3” and everything else stayed the same • 483x10-3A • 32x106V • 2x10-9A • 3.4x10-12s • .350x103Ω • 42x10-6V 483mA 32MV 2nA 3.4ps .350kΩ 42uV This can be simplified to just 350 Ω

  14. More practice problems -Converting regular numbers to scientific notation. • Convert 4578 to scientific notation • Convert .00009 to scientific notation • Convert 4.56 to scientific notation • What does 6.4 x 10^0 = ? 4.578 x 103 9x10-5 4.56x100 6.4 x 1 = 6.4 Notice in the above example 9x10-5 cannot be converted to a prefix very easily because there is no prefix for -5. So it is useful to convert this number to one that does have a prefix. 9x10-5 = .00009 = .000090 = 90 x 10-6 = 90u What we just did was convert scientific notation to engineering notation!!! (Go ahead and write home)

  15. So what is the difference between scientific notation and engineering notation? • In scientific notation there is always only one digit or number in front of the decimal and everything else is behind the decimal. • Ex: 9.54 x 10-5 • In Engineering notation the exponent is always a multiple of 3. • Ex: 95.4 x 10-6 • Notice -6 is a multiple of 3

  16. Notice all prefixes are multiples of 3

  17. We will be using engineering notation for electronics courses because it is useful in converting to prefixes. • Convert the following to engineering notation and then to its corresponding prefix • .00043A • 23x10-2V • 67x107s • .00000783m = 430 x 10-6A = 430uA = .23V = 230x10-3V = 230mV = 670000000s = 670x106s = 670Ms = 7.83x10-9s = 7.83nm

  18. Random Video of the Day!

  19. Get out your Calulators • First put your calculator in Engineering Notation • Press 2nd F • Press SET UP • Press 1 for FSE (Fixed Scientific Engineering • Press 2 for Engineering Notation • Enter 9 so it shows the most amount of precision • It says ENG on the left side of the screen now. • If you ever want your calculator to show normal looking numbers as answers again, you’ll have to go through this process and press 0 for fixed numbers at the last step.

  20. Enter 567000 and press =. • Notice it automatically put it into Engineering Notation. • It shows 567E3 • E is an abbreviated way of saying “x10^” • 567E3 = 567 x103 • Now press .0000004 and press enter • You may need to press the Change button to convert it from a fraction • It shows 400E-9. • Convert this to a prefix • 400n!!!!

  21. Look on Page 21 of your book • Throughout the text book, anytime we will encounter a new feature using the calculator, it will tell you the buttons to press to perform the particular operation.

  22. Convert to a prefix using calculator • .000056V • 5430000A • 4300Ω • .00076s = 56uV = 5.43MA = 4.3kΩ = 760us

  23. Using a Calculator for this stuff3 ways to enter these numbers • Entering 5.4x103 • Just enter 5400 • 5.4x 3 • 5.4 3 is the same thing as “x10^” Sometimes 5.4x103 can be expressed as 5.4E3. This is the same thing as 5.4 EXP 3 EXP 10x EXP

  24. Converting between units • Many times it is useful to convert from one prefix to another. ie: uA to nA • Convert 43uA to nA • 43uA = 43000nA • To do this we will use 2 rules. WRITE THESE DOWN! • If you are going from a larger exponent to a smaller exponent, then you move the decimal to the right • If you are going from a smaller exponent to a larger exponent, then you move the decimal to the left

  25. - If you are going from a larger exponent to a smaller exponent, then you move the decimal to the right.- If you are going from a smaller exponent to a larger exponent, then you move the decimal to the left 43 Convert 43 mV into _______uV .043V Convert 14kV into ________MV Convert 72GV into _______nV 43.uV = 43uV .014 72,000,000,000,000,000,000V

  26. - If you are going from a larger exponent to a smaller exponent, then you move the decimal to the right.- If you are going from a smaller exponent to a larger exponent, then you move the decimal to the left Now convert to Engineering Notation 10 10x103A 1.5 1.5x106Ω 1.2 1.2x103Hz 5100 5100 x10-6A 0.04 0.04x10-3A 1 1x103W 1500 1500x10-12F .15 .15x103V .25 .25x106W 3700 3700x103Ω

  27. Using the table. You have this as a handout Convert 1 microsecond into ________seconds Convert 2834.5 nanoseconds into ________microseconds Convert .4 milliohms into __________ ohms .000001 2.8345 .0004

  28. Explaining Handout – This handout may be used on tests, but no writing may be on it. • Handout

  29. Units Worksheet • Lets do together 1, 2, 10, 11, 17, 22 • Go ahead and finish the rest of the worksheet on your own. If you don’t finish it in class it is homework. • Its due on Monday

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