ELECTRICALFUNDAMENTALS          TOPIC 1Fundamental And Derived Units                                1
Learning ObjectivesAt the conclusion of this section, students should beable to:  Identify the basic units of measurement...
ResourcesHampson & Hanssen, “Electrical Trade Principles – A practical  approach”    Pgs 2 – 5, 15 – 25 & 421 including re...
TRANSPOSITION                4
TRANSPOSITIONaddition/subtraction                       5
TRANSPOSITIONmultiply/divide                  6
TRANSPOSITION – multiply/divide                   7
TRANSPOSITION – mixed     operations                        8
TRANSPOSITION – mixed     operations                        9
TRANSPOSITION – mixed operations                    10
TRANSPOSITION – roots                        11
TRANSPOSITION – roots                        12
SubstitutionTake the electrical quantities of: Power (P),Voltage (V), Current (I) and Resistance (R). Thereare two equatio...
Substitution                V       IRSubstituting IR for V in the power equation,              P      I R I              ...
Base Units            • The Systeme Internationale’ (SI) is the                   International Metric System            T...
SI Derived Units    The six basic units are not sufficient to        act for all situations that arise in                 ...
SI Derived Units            The units used can be subdivided                   into three groups:      mechanical, electri...
Derived Quantities Velocity (distance traveled in a given time) Acceleration (the rate of change in velocity) Force (th...
Derived Mechanical Units                Unit        Symbol                Quantity   Symbol                Force         F...
Derived Electrical Units               Unit       Symbol             Quantity   Symbol              Power         P       ...
Multiples And Submultiples         In practical cases some SI values are       inconveniently large or small, In order to ...
Multiples and Submultiples                 Tera    1012    T                 giga    109     G                mega     106...
2/17/2012   Revision02   23
Scientific Notation• Another method of overcoming cumbersome  rows of figures is to notate numbers to a  value between 1 a...
Examples:                    • Given: 1.015 x 10 -8             – Answer: 0.00000001015 (8 places to left)            – Ne...
Examples• Express in standard form                     • 1.09 x 10 3                    • 4.22715 x 10 8                  ...
To change from scientific notation        to standard form:  • Move decimal point to right for positive              expon...
Express in correct scientific                     notation                    0.0000568                       321         ...
PREFIXES           29
PREFIXES           30
Abbreviations and Conventions(shortened names for things)      (agreed standard ways to do or                             ...
Abbreviations and Conventions2. When writing numbers above 999, they   should be clustered into groups of three.   For exa...
Abbreviations and Conventions5. A leading zero should precede a decimal value.    For example            0.351 and not .35...
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E104 B Topic 1

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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
  5. 5. TRANSPOSITIONaddition/subtraction 5
  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

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