1a_measurements unit.pdf

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ELECTRIC CIRCUIT ANALYSIS

CHAPTER 1

Electric Circuit Analysis

STB 11303


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OBJECTIVES

Become familiar with the SI system of units usedthroughout the electrical/electronics industry.

Understand the importance of power of ten and

how to work with them.

Understand the use of scientific notation and

engineering notation.

Be able to convert any quantity in any system of

units to another system.

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SI Unit

SI units are the unit that had been adopted by all nations.

Initiated during The International Bureau of Weights and Measures,

located in Sevres, France in 1960, attended by representative from allnations of the world.

Le Systeme International dUnites(International System of Units)

Being adopted by Institute of Electrical and Electronics Engineers, Inc in1965 and by United States of America Standards Institute.

1967 is accepted as standard for all scientific and engineering literature.

(abbreviated SIfrom French: Systme international d'units)

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http://en.wikipedia.org/wiki/French_languagehttp://en.wikipedia.org/wiki/French_language


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Base Quantity Base Unit

Name Symbol Name Symbol

W Joule J

Iv

Time

Length

Mass

Temperature

Energy

Amount of Substance

Luminous Intensity

t

l

m

T ,

n

second

metrekilogram

kelvin

mole

candela

s

mkg

K

mol

cd

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Electrical Quantity Base Unit

Name Symbol Name Symbol

Volt

Frequency f Hertz

Resistance R Ohm

Capacitance C

P

Current

Voltage

Inductance

Power

I

L

Ampere

Farad

Henry

Watt

A

VHz

F

H

W

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Derived

Quantity

Derivation Unit

Speed Distance / time ms-1

Acceleration Speed / Time ms-2

Force Mass x Acceleration Kgms-2

(Newton)

Work Force x Distance Nm

Power Work / Time Watt

Pressure Force / Area Pa (Pascal)

Density Mass / Volume Kgm-3

Charge Current x Time C

(Coulomb)

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SI Prefixes

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SI Units Table

ENGINEERING NOTATION PREFIXES

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Product for Powers of Ten

)mn(mn

)mn(

m

n

)mn(mn

10)10(

1010

10

10)10)(10(

)(

)(

)(

)(

)(

)(

mnmmn

mn

m

n

mnmn

nnn

10A10A

10B

A

10B

10A

10BA10B10A

10BA10B10A

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Power of Ten

3

3

n

n

1010

1

1000

1

Example

1010

1

5

5

m

m

1010

1

00001.0

1Example

1010

1

10


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The notation used to represent numbers

that are integer powers of ten is as follows:

Examples;

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FIXED POINT

FLOATING POINTThe decimal point require decimal appears in all location in display.

The fixed point format require the decimal point appear in same place all

the time.

33333333303

1.

33303

1.

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SCIENTIFIC NOTATIONRequire decimal point appear directly after the first digit greater than or equal to

1 but less than 10

All powers of ten must be multiples of 3, and mantissa(multiplier) must be greater

than or equal to 1 but less than 1000.

ENGINEERING NOTATION

1E3331033333303

1 1

...

3E333310333333333303

1 3

...

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Practice : Examples

Write in Scientific Notation and Engineering Notation.

Solution :

Scientific Notation : 6.25E 2

Engineering Notation : 62.50E 3

16

1

0625016

1.

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Conversion between System of Units

Example :

a) Determine the number of minutes in a half day .

b) Convert 0.24m to cm.

c) Determine the speed in miles per hour of a competitor

who can run a mile in 4 minutes.d) In Europe, Canada and many countries, the speed limit

is posted in kilometers per hour. How fast in miles per

hour is 100km/h?

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Application of Units Conversion

Speed of light = 299,792,458 m/s

1 Kilogram = 1000 X 1 cubic cm of pure water at 4oC

1 Second = 9,192,631,770 periods of electromagnetic radiation emitted by celsium atom

1 cubic of cooper at room temperature consist of 1.4 X 1024

free electrons

1 Coulomb of charge equal to 6.242 X 1018 electrons

1 Ampere = flow of 1 Coulomb in ONE second

1 Volt = potential difference to move 1 Coulomb of charge, the energy used is 1 Joule (J)

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CONDUCTORS AND INSULATORS conductorsare those materials that permit a generous flow

of electrons (electric current flows) with very little external

force (voltage) applied

In addition, good conductors typically have only oneelectron in the valence (most distant from the nucleus) ring

Example; copper wire, iron, silver, aluminum, gold

Insulators are materials that resists electric current and also

does not readily allow the passage of heat or sound

Thus, this substance is generally used as an insulation for heat orcold, current, sound.

Example; plastic, rubber, PVC tube, cloth, carbon fiber


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Relative conductivity of various materials

Conductors Resistivity and Relative Conductivity Properties

Resistivity (p) of various materials

When Resistivity (Current Blocking) is HIGH (), then Conducting (Current Flow) is LOW ()

Important Note ***

Th Eff t f C d t d I l t


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The Effect of Conductors and Insulators

properties to Current Flows

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Different wires placed across the same two battery terminals allow different amounts of

charge to flow between the terminals.

Many factors, such as the density, mobility, and stability characteristics of a material,account for these variations in charge flow.

Example: Battery Life Factors

The most important piece of

data for any battery is thevoltage rating and is its

ampere-hour (Ah) rating

The ampere-hour (Ah) rating

provides an indication of how

longa battery of fixed voltage

able to supply a particularcurrent

Ampere-hour rating (capacity) versus drain current for an Energizer D cell.

Hours duration

reduced for

higher usage of

current


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Temperature Effects to Electric Current Source

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The previous section made it clearthat the life of a battery is directlyrelated to the magnitude of thecurrent drawn from the supplyvoltage

We also known that temperatureisalso effectingthe structure ofmaterial and the material resistivityto electric flows

Typical battery life plot for different

temperature range is shown

Ampere-hour rating (capacity) versus temperature for an Energizer D cell.

0oCelcius

25oCelcius


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21

Internal construction of the 9 V

dc supply adapter

Insulator

Conductor

Applications of Conductors and Insulators

Insulator

A group of conductor wires

A single

conductor wire


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AMMETERS AND VOLTMETERS

It is important to be able to measure the current and voltage levels of an operating

electrical system to check its operation, isolate malfunctions (trouble shooting),and investigate effects of any electrical problems

Ammeters are used to measure current flow levels in a closed circuit

Voltmeters, are used to measure potential difference between twopoints


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Voltmeter connection for an up-scale (+) reading.

VOLTMETERS = Voltage Meters

measure potential difference between two points


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AMMETERS = Ampere Meters

Ammeter connection for an up-scale (+) reading.

measure current flow levels in a closed circuit


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Digital multimeter(DMM).

Digital MultimetersUse to measure Voltage, Current, Resistance, Connectivity between 2 points

1a_measurements unit.pdf

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