Upcoming SlideShare
×

# E104 B Topic 1

1,251 views

Published on

0 Likes
Statistics
Notes
• Full Name
Comment goes here.

Are you sure you want to Yes No
• Be the first to comment

• Be the first to like this

Views
Total views
1,251
On SlideShare
0
From Embeds
0
Number of Embeds
123
Actions
Shares
0
22
0
Likes
0
Embeds 0
No embeds

No notes for slide

### E104 B Topic 1

1. 1. ELECTRICALFUNDAMENTALS TOPIC 1Fundamental And Derived Units 1
2. 2. Learning ObjectivesAt the conclusion of this section, students should beable to:  Identify the basic units of measurement  Define and use the SI derived units for force, pressure, energy, work, temperature and power  Convert units to multiple and sub-multiple units  Transpose a given equation for any variable in the equation  Perform basic calculations of electrical and related mechanical quantities given any combination of units, multiple units or sub- multiple units. 2
3. 3. ResourcesHampson & Hanssen, “Electrical Trade Principles – A practical approach” Pgs 2 – 5, 15 – 25 & 421 including review questionsChisholm Moodle E Learning 3
4. 4. TRANSPOSITION 4
6. 6. TRANSPOSITIONmultiply/divide 6
7. 7. TRANSPOSITION – multiply/divide 7
8. 8. TRANSPOSITION – mixed operations 8
9. 9. TRANSPOSITION – mixed operations 9
10. 10. TRANSPOSITION – mixed operations 10
11. 11. TRANSPOSITION – roots 11
12. 12. TRANSPOSITION – roots 12
13. 13. SubstitutionTake the electrical quantities of: Power (P),Voltage (V), Current (I) and Resistance (R). Thereare two equations that use these quantities, theyare: P = V x I and V = I x RSuppose we want to calculate power when onlycurrent (I) and resistance (R) is known.Substitution will enable power to be calculated. 13
14. 14. Substitution V IRSubstituting IR for V in the power equation, P I R I 2 I R 14
15. 15. Base Units • The Systeme Internationale’ (SI) is the International Metric System There are 6 Base Units in the SI system Unit Symbol Quantity Symbol Length l Metre m Time s Second s Mass m Kilogram kg Current I Ampere A Temperature T Kelvin K Light I candela cd2/17/2012 Revision02 15
16. 16. SI Derived Units The six basic units are not sufficient to act for all situations that arise in measurement. Derived units are used for all non-basic situations. Most derived units use the three basic units of length, mass and time in various combinations..2/17/2012 Revision02 16
17. 17. SI Derived Units The units used can be subdivided into three groups: mechanical, electrical and magnetic although it must be realised there are many more examples than those listed2/17/2012 Revision02 17
18. 18. Derived Quantities Velocity (distance traveled in a given time) Acceleration (the rate of change in velocity) Force (the physical action capable of moving a body) Torque (twisting force eg produced by a motor) Pressure (force per unit area) Electrical charge (1 Amp flowing for 1 second) Voltage (electrical pressure) Resistance (opposition to current flow) Energy (the capacity to do work) Work (force acting through a distance) Power (rate of doing work) 18
19. 19. Derived Mechanical Units Unit Symbol Quantity Symbol Force F Newton N Pressure P Pascal Pa Energy & Work W Joule J2/17/2012 Revision02 19
20. 20. Derived Electrical Units Unit Symbol Quantity Symbol Power P watt W Frequency F hertz Hz Potential V volt V Charge Q coulomb C Capacitance C farad F2/17/2012 Revision02 20
21. 21. Multiples And Submultiples In practical cases some SI values are inconveniently large or small, In order to choose values that are convenient to handle, multiples or submultiples are used. For example, if the resistance of an electrical installation is measured at 15 000 000 ohms, it is more convenient to refer to this value as 15 megohms.2/17/2012 Revision02 21
22. 22. Multiples and Submultiples Tera 1012 T giga 109 G mega 106 M kilo 103 k milli 10-3 m micro 10-6 nano 10-9 n pico 10-12 p2/17/2012 22
23. 23. 2/17/2012 Revision02 23
24. 24. Scientific Notation• Another method of overcoming cumbersome rows of figures is to notate numbers to a value between 1 and 10 multiplied by 10 to some power.• For example, 6 800 000 can be expressed as • 6.8 x 106 and • 1250 as 1.25 x 1032/17/2012 Revision02 24
25. 25. Examples: • Given: 1.015 x 10 -8 – Answer: 0.00000001015 (8 places to left) – Negative exponent move decimal to the left – Given: 5.024 x 10 -3 – Answer: 5,024 (3 places to the right) – Positive exponent move decimal to the right2/17/2012 Revision02 25
26. 26. Examples• Express in standard form • 1.09 x 10 3 • 4.22715 x 10 8 • 3.078 x 10 – 4 • 9.004 x 10 – 2 • 5.1874 x 10 22/17/2012 Revision02 26
27. 27. To change from scientific notation to standard form: • Move decimal point to right for positive exponent of 10 • Move decimal point to left for negative exponent of 102/17/2012 Revision02 27
28. 28. Express in correct scientific notation 0.0000568 321 64 960 000 0.07085 61 5002/17/2012 Revision02 28
29. 29. PREFIXES 29
30. 30. PREFIXES 30
31. 31. Abbreviations and Conventions(shortened names for things) (agreed standard ways to do or write things)1. There should be a space between the numeric value and the unit symbol. For example five milliamps is written as 5 mA and not 5mA(A ‘hard’ space in a typed document will prevent this; 240 V i.e. the unit symbol appearing on the next line.) 31
32. 32. Abbreviations and Conventions2. When writing numbers above 999, they should be clustered into groups of three. For example, 1 000 or 20 000 or 0.000 006 78 and not 1000 or 20000 or 0.00000678 (This reduces the chance of mis-reading a number’s size by mis-counting zero’s) 32
33. 33. Abbreviations and Conventions5. A leading zero should precede a decimal value. For example 0.351 and not .351 (This makes it easier to recognise a missing decimal point, for instance, on a well-used drawing 0 351 would be obvious but 351 could lead to a major error!) 33