chapter 1staff.uob.edu.bh/files/600435156_files/ecf_1.pdf · chapter 1 quiz 3. in scientific...

Electric Circuits Fundamentals - Floyd © Copyright 2007 Prentice-Hall

Chapter 1Chapter 1

Chapter 1


Chapter 1Chapter 1Summary

Scientific and Engineering Notation

Very large and very small numbers are represented with scientific and engineering notation.

47,000,000 = 4.7 x 107 (Scientific Notation)

= 47 x 106 (Engineering Notation)



Scientific and Engineering Notation

0.000 027 = 2.7 x 10-5 (Scientific Notation)

= 27 x 10-6 (Engineering Notation)

0.605 = 6.05 x 10-1 (Scientific Notation)

= 605 x 10-3 (Engineering Notation)



Metric Conversions

Most scientific calculators can be placed in a mode that will automatically convert any decimal number entered into scientific notation or engineering notation.

Numbers in scientific notation can be entered in a scientific calculator using the EE key.



SI Fundamental Units

lengthmasstimeelectric currenttemperatureluminous intensityamount of substance

meterkilogramsecondampereKelvincandelamole

mkgsAKcdmol

Quantity Unit Symbol



Some Important Electrical Units

Except for current, all electrical and magnetic units are derived from the fundamental units. Current is a fundamental unit.Quantity Unit Symbol

currentchargevoltageresistancepower

amperecoulombvoltohmwatt

ACVΩW



Engineering Metric Prefixes

P

T

G

M

k

peta

tera

giga

mega

kilo

1015

1012

109

106

103

Can you name the prefixes and their meaning?



Engineering Metric Prefixes

m

µ

n

p

f

milli

micro

nano

pico

femto

10-3

10-6

10-9

10-12

10-15

Can you name the prefixes and their meaning?



Metric Conversions

When converting from a larger unit to a smaller unit, move the decimal point to the right. Remember, a smaller unit means the number must be larger.

0.47 MΩ = 470 kΩ

Larger number

Smaller unit



Metric Conversions

When converting from a smaller unit to a larger unit, move the decimal point to the left. Remember, a larger unit means the number must be smaller.

10,000 pF = 0.01 µF

Smaller number

Larger unit



Metric Arithmetic

When adding or subtracting numbers with a metric prefix, convert them to the same prefix first.

10,000 Ω + 22 kΩ =

10,000 Ω + 22,000 Ω = 32,000 Ω

Alternatively,10 kΩ + 22 kΩ = 32 kΩ



Metric Arithmetic

When adding or subtracting numbers with a metric prefix, convert them to the same prefix first.

200 µΑ + 1.0 mA =

200 µA + 1,000 µA = 12,000 µA

Alternatively,0.200 mΑ + 1.0 mA = 1.2 mA



Error, Accuracy, and Precision

Experimental uncertainty is part of all measurements. Error is the difference between the true or best accepted value and the measured value. Accuracy is an indication of the range of error in a measurement.

Error

Precision is a measure of repeatability.

Precise, but not accurate.



Significant Digits

When reporting a measured value, one uncertain digit may be retained but other uncertain digits should be discarded. Normally this is the same number of digits as in the original measurement.

Assume two measured quantities are 10.54 and 3.92. If the larger is divided by the smaller, the answer is 2.69 becausethe answer has the same uncertainty as the original measurement.



Significant Digits

Rules for determining if a reported digit is significant are:

1. Nonzero digits are always considered to be significant.

2. Zeros to the left of the first nonzero digit are never significant.

3. Zeros between nonzero digits are always significant.

4. Zeros to the right of the decimal point for a decimal number aresignificant.

5. Zeros to the left of the decimal point with a whole number may or may not be significant depending on the measurement.



Rounding numbersRounding is the process of discarding meaningless digits. Rules for rounding are:

1. If the digit dropped is greater than 5, increase the last retained digit by 1.

2. If the digit dropped is less than 5, do not change the last retained digit.

3. If the digit dropped is 5, increase the last retained digit ifit makes it even, otherwise do not. This is called the "round-to-even" rule.



Electrical SafetySafety is always a concern with electrical circuits. Knowing the rules and maintaining a safe environment is everyone’s job. A few important safety suggestions are:

• Do not work alone, or when you are drowsy.• Do not wear conductive jewelry.• Know the potential hazards of the equipment you are

working on; check equipment and power cords frequently.• Avoid all contact with energized circuits; even low voltage

circuits.• Maintain a clean workspace.• Know the location of power shutoff and fire extinguishers.• Don’t have food or drinks in the laboratory or work area.


Chapter 1Chapter 1

Engineering notation

Exponent

Metric prefix

Power of ten

A system for representing any number as a one-, two-, or three-digit number times a power of ten with an exponent that is a multiple of three.

The number to which a base is raised.

A symbol that is used to replace the power of ten in numbers expressed in scientific or engineering notation.

Key Terms

A numerical representation consisting of a base of 10 and an exponent; the number 10 raised to a power.


Chapter 1Chapter 1

Scientific notation

Accuracy

Precision

Significant digit

An indication of the range of error in a measurement.

A measure of the repeatability (consistency) of a series of measurements.

A digit known to be correct in a number.

A system for representing any number as a number between 1 and 10 times a power of ten.

Key Terms


Chapter 1Chapter 1Quiz

1. A number written as 2.59 x 107 is said to be in

a. scientific notation

b. engineering notation

c. both of the above

d. none of the above



2. The electrical unit that is fundamental is the

a. volt

b. ohm

c. coulomb

d. ampere



3. In scientific notation, the number 0.000 56 is written

a. 5.6 x 104

b. 5.6 x 10-4

c. 56 x 10-5

d. 560 x 10-6



4. In engineering notation, the number 0.000 56 is written

a. 5.6 x 104

b. 5.6 x 10-4

c. 56 x 10-5

d. 560 x 10-6



5. The metric prefix nano means

a. 10-3

b. 10-6

c. 10-9

d. 10-12



6. The metric prefix pico means

a. 10-3

b. 10-6

c. 10-9

d. 10-12



7. The number 2700 MW can be written

a. 2.7 TW

b. 2.7 GW

c. 2.7 kW

d. 2.7 mW



8. The value 68 kΩ is equal to

a. 6.8 x 104 Ω

b. 68, 000 Ω

c. 0.068 MΩ

d. All of the above



9. The sum of 330 mW + 1.5 W is

a. 331.5 mW

b. 3.35 W

c. 1.533 W

d. 1.83 W



10. Precision is a measurement of

a. the total error in a series of measurements

b. the consistency of a series of measurements

c. both of the above

d. none of the above


Chapter 1Chapter 1

Answers:

1. a

2. d

3. b

4. d

5. c

6. d

7. b

8. d

9. d

10. b

Quiz

chapter 1staff.uob.edu.bh/files/600435156_files/ecf_1.pdf · chapter 1 quiz 3. in scientific...

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