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**Prefixes, Units and Unit Conversion**

Chapter 2 Prefixes, Units and Unit Conversion

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**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 = 5 x 10-6 = 5 x 1/(106) = 5x =

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**Scientific Units Parameter Unit Length Mass Time For Electronics**

Voltage Current Resistance Meter [m] Kilogram [kg] Second [s] Volt [V] Amp [A] Ohm [Ω]

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Other Units

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**Prefixes How many meters are there in a kilometer?**

1000 How many milliseconds are there in a second? How many bytes are there in a Gigabyte? 1,000,000,000

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**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

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**Prefixes we’ll use in Elec50A**

Abbrev. Example What it means Scientific Notation Giga G Gm x1,000,000,000 x109 Mega M MV x1,000,000 x106 Kilo k kA x1,000 x103 Unit Base - S x1 x100 Milli m mg x.001 x10-3 Micro Or u uΩ x x10-6 Nano n ns x x10-9 Pico p pA x x10-12

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

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**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)?

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**Quick Prefix Quiz (cont.)**

How small is a nA 1 billionth or A or 10-9 How small is a uΩ? 1 millionth or Ω or 10-6 How big is a pV? 1 trillionth of a volt or V

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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 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

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**Write the following in scientific notation:**

3mV 18kV 43ms 2.1GA 30uA 57ps 3x10-3V 18x103V 43x10-3s 2.1x109A 30x10-6A 57x10-12s

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**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

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**More practice problems - Converting regular numbers to scientific notation.**

Convert 4578 to scientific notation Convert 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 = = = 90 x 10-6 = 90u What we just did was convert scientific notation to engineering notation!!! (Go ahead and write home)

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**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

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**Notice all prefixes are multiples of 3**

Abbrev. Example What it means Scientific Notation Giga G Gm x1,000,000,000 x109 Mega M MV x1,000,000 x106 Kilo k kA x1,000 x103 Unit Base - S x1 x100 Milli m mg x.001 x10-3 Micro Or u uΩ x x10-6 Nano n ns x x10-9 Pico p pA x x10-12

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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 m = 430 x 10-6A = 430uA = .23V = 230x10-3V = 230mV = s = 670x106s = 670Ms = 7.83x10-9s = 7.83nm

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Random Video of the Day!

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**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.

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Enter 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 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!!!!

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**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.

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**Convert to a prefix using calculator**

4300Ω .00076s = 56uV = 5.43MA = 4.3kΩ = 760us

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**Using a Calculator for this stuff 3 ways to enter these numbers**

Entering 5.4x103 Just enter 5400 5.4x 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 10x EXP

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**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

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**Convert 43 mV into _______uV .043V Convert 14kV into ________MV **

- 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

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- 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

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**Using the table. You have this as a handout**

Convert 1 microsecond into ________seconds Convert nanoseconds into ________microseconds Convert .4 milliohms into __________ ohms 2.8345 .0004

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

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**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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