Chapter 2 Powerpoint

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Chapter 2
Prefixes, Units and Unit Conversion
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

Scientific Units
Parameter
 Length
 Mass
 Time
Unit
Meter [m]
Kilogram [kg]
Second [s]
For Electronics
 Voltage
Volt [V]
 Current
Amp [A]
Ohm [Ω]
 Resistance
Other Units
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
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

Prefixes we’ll use in Elec50A
Prefix
Abbrev.
Example
What it means
Scientific
Notation
Giga
G
Gm
x1,000,000,000
Mega
M
MV
x1,000,000
Kilo
k
kA
x1,000
Unit Base
-
S
x1
Milli
m
mg
x.001
Micro
 Or u
uΩ
x.000001
Nano
n
ns
x.000000001
Pico
p
pA
x.000000000001
x109
x106
x103
x100
x10-3
x10-6
x10-9
x10-12
In your book they show other
prefixes we won’t use much if at all.
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
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
3 ways to write a number
1 million volts
1 thousandth of an amp
1 millionth of an ohm
1 billion grams
5 thousand meters
1 second
Regular Way
Using Prefixes
Scientific Notation
1,000,000 V
.001 A
.000001 Ω
1MV
1mA
1uΩ
1x106 V
1x10-3 A
1x10-6 Ω
1,000,000,000 g
5000 m
1s
1Gg
5km
1s
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
Write the following in scientific
notation:
3mV
 18kV
 43ms
 2.1GA
 30uA
 57ps

3x10-3V
18x103V
43x10-3s
2.1x109A
30x10-6A
57x10-12s
Write the following using prefixes
 483x10-3A
32x106V
 2x10-9A
 3.4x10-12s
 .350x103Ω
 42x10-6V

483mA
32MV
2nA
3.4ps
.350kΩ
42uV
Notice “m” replaced all
of “x10-3” and everything
else stayed the same
This can be
simplified to just
350 Ω
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)
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
Notice all prefixes are multiples of 3
Prefix
Abbrev.
Example
What it means
Scientific
Notation
Giga
G
Gm
x1,000,000,000
Mega
M
MV
x1,000,000
Kilo
k
kA
x1,000
Unit Base
-
S
x1
Milli
m
mg
x.001
Micro
 Or u
uΩ
x.000001
Nano
n
ns
x.000000001
Pico
p
pA
x.000000000001
x109
x106
x103
x100
x10-3
x10-6
x10-9
x10-12
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
-6A = 430uA
=
430
x
10
 .00043A
= .23V = 230x10-3V = 230mV
 23x10-2V
6s = 670Ms
7
=
670000000s
=
670x10
 67x10 s
-9s = 7.83nm
=
7.83x10
 .00000783m

Random Video of the Day!
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.










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!!!!
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.
Convert to a prefix using calculator
.000056V
 5430000A
 4300Ω
 .00076s

= 56uV
= 5.43MA
= 4.3kΩ
= 760us
Using a Calculator for this stuff
3 ways to enter these numbers
Entering 5.4x103
1. Just enter 5400
2. 5.4x 10x 3
3. 5.4 EXP 3

EXP
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
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

- 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 43.uV = 43uV
.014
Convert 14kV into ________MV
Convert 72GV into _______nV
72,000,000,000,000,000,000V
- 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
1.5
1.2
5100
0.04
1
1500
.15
.25
3700
10x103A
1.5x106Ω
1.2x103Hz
5100 x10-6A
0.04x10-3A
1x103W
1500x10-12F
.15x103V
.25x106W
3700x103Ω
Using the table.You have this as a handout
Convert 1 microsecond into ________seconds
.000001
2.8345
Convert 2834.5 nanoseconds into ________microseconds
.0004
Convert .4 milliohms into __________
ohms
Explaining Handout – This handout
may be used on tests, but no writing
may be on it.

Handout
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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