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1.4 understanding measurement

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1.4 understanding measurement

  1. 1. Chapter 1 Introduction To Physics 1.4Understanding Measurement www.myfunphysicsworld.blogspot.com
  2. 2. www.myfunphysicsworld.blogspot.com
  3. 3. Learning Outcomes Measure physical quantities using appropriate instruments Explain :1. accuracy, consistency, sensitivity2. Types of experimental error Use appropriate technique to reduce error www.myfunphysicsworld.blogspot.com
  4. 4. Measuring Instruments Metre Rule Measuring tape Micrometer Screw Gauge Vernier Calipers Stop watch Thermometer Ammeter Triple beam balance Spring balance www.myfunphysicsworld.blogspot.com
  5. 5. Accuracy How close the value of the measurement to the actual value www.myfunphysicsworld.blogspot.com
  6. 6. ConsistencyThe consistency of a measuringinstrument is its ability toregister the same readingwhen a measurement isrepeated. www.myfunphysicsworld.blogspot.com
  7. 7. Sensitivity The instruments ability to detect a small change in the quantity to be measured Responds faster, by a larger extend to small variations in quantity measured www.myfunphysicsworld.blogspot.com
  8. 8. Accuracy www.myfunphysicsworld.blogspot.com
  9. 9. www.myfunphysicsworld.blogspot.com
  10. 10. www.myfunphysicsworld.blogspot.com
  11. 11. Consistency www.myfunphysicsworld.blogspot.com
  12. 12. ConsistencyThe consistency of a measuringinstrument is its ability toregister the same readingwhen a measurement isrepeated. www.myfunphysicsworld.blogspot.com
  13. 13. Consistency Very Consistent : readings are all the same everytime measured www.myfunphysicsworld.blogspot.com
  14. 14. www.myfunphysicsworld.blogspot.com
  15. 15. www.myfunphysicsworld.blogspot.com
  16. 16. How to measureconsistency? Calculate Relative Deviation High consistency: Smaller value of relative deviation www.myfunphysicsworld.blogspot.com
  17. 17. Deviation & RelativeDeviationA deviation is the difference betweena measured value and its meanvalue or the average value. www.myfunphysicsworld.blogspot.com
  18. 18. READING CONSISTENCY S AVERAGE 1 0.5 = 0.5 + 0.4 + 0.5+0.3+0.4 5 2 0.4 = 0.42 3 0.5 DEVIATION (1st Reading) 4 0.3 = 0.42 – 0.5 = 0.08 5 0.41. AVERAGE2. DEVIATION3. AVERAGE DEVIATION4. RELATIVE DEVIATION : average deviation x 100% www.myfunphysicsworld.blogspot.com
  19. 19. www.myfunphysicsworld.blogspot.com
  20. 20. READINGS Deviation 1 0.5 0.08 2 0.4 0.02 3 0.5 0.08 4 0.3 0.12 5 0.4 0.02Average 0.42 0.064 = 0.06 RELATIVE DEVIATION : = average deviation x 100% average = 0.06/0.42 x 100% = 14.29 % www.myfunphysicsworld.blogspot.com
  21. 21. 4amanah until here20/01 www.myfunphysicsworld.blogspot.com
  22. 22. The consistency of a measuring instrument can be improved by:(a) eliminating parallax measurement.(b) exercising greater care and effort when taking readings.(c) using an instrument which is not defective www.myfunphysicsworld.blogspot.com
  23. 23. Sensitivity www.myfunphysicsworld.blogspot.com
  24. 24. Sensitivity The instruments ability to detect a small change in the quantity to be measured www.myfunphysicsworld.blogspot.com
  25. 25. Appropriate Instrument Musthave:Appropriate sensitivity www.myfunphysicsworld.blogspot.com
  26. 26. Choosing AppropriateInstrument Must consider Magnitude of the quantity Should not exceed the maximum and minimum capasity of the instrument www.myfunphysicsworld.blogspot.com
  27. 27. Sensitivity The smaller the change which can be measured by the instrument, The more sensitive the instrument is www.myfunphysicsworld.blogspot.com
  28. 28. www.myfunphysicsworld.blogspot.com
  29. 29. How to increase thesensitivity? Narrow capillary Thin walled-bulb www.myfunphysicsworld.blogspot.com
  30. 30. www.myfunphysicsworld.blogspot.com
  31. 31. Errors In Measurements Two types of experimental errors:1. Systematic errors2. Random errors www.myfunphysicsworld.blogspot.com
  32. 32. Systematic errors www.myfunphysicsworld.blogspot.com
  33. 33. Systematics errors Due to1. the error in calibration of instrument which makes it defective2. Zero error* of the instrument Zero error – the pointer of the instrument does not return to zero when not in use www.myfunphysicsworld.blogspot.com
  34. 34. Systematics errors Will lead to a decrease in accuracy Always occur with the same value when we measure using the same instrument in the same way Readings taken are always larger or always smaller than the true value www.myfunphysicsworld.blogspot.com
  35. 35. Can we eliminate thesystematic error by repeatingthe measurement andaveraging out the result? No! Cannot! Only can by: calibrating or doing adjustment to the instrument www.myfunphysicsworld.blogspot.com
  36. 36. Random errors www.myfunphysicsworld.blogspot.com
  37. 37. Random errors Due to1. the carelessness of the observer when making measurement (parallax error)2. Sudden change of ambient factor (temperature, air circulation) Will lead to a decrease in consistency www.myfunphysicsworld.blogspot.com
  38. 38. www.myfunphysicsworld.blogspot.com
  39. 39. accurac ywww.myfunphysicsworld.blogspot.com
  40. 40. VERNIER CALLIPERS www.myfunphysicsworld.blogspot.com
  41. 41. www.myfunphysicsworld.blogspot.com
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  44. 44.  What is the accuracy of a) main scale b) vernier scale www.myfunphysicsworld.blogspot.com
  45. 45. www.myfunphysicsworld.blogspot.com
  46. 46.  Reading = 3.2 + 0.04 = 3.24 cm www.myfunphysicsworld.blogspot.com
  47. 47. MICROMETER SCREWGAUGE www.myfunphysicsworld.blogspot.com
  48. 48. www.myfunphysicsworld.blogspot.com
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  50. 50. What is the reading? www.myfunphysicsworld.blogspot.com
  51. 51. Reading = 2.0 + 0.22 = 2.22 mm www.myfunphysicsworld.blogspot.com
  52. 52. What is the reading? www.myfunphysicsworld.blogspot.com
  53. 53. Reading = 2.5 + 0.22 = 2.72 mm www.myfunphysicsworld.blogspot.com
  54. 54. ZERO ERROR www.myfunphysicsworld.blogspot.com
  55. 55. www.myfunphysicsworld.blogspot.com
  56. 56. 0 0Zero Error = negative = - (0.10 – 0.06) = - 0.04 cm www.myfunphysicsworld.blogspot.com
  57. 57. 0 main 0 vernierZero Error = positive = +0.05 cm www.myfunphysicsworld.blogspot.com
  58. 58. 4 amanah until here27 jan-reading msg already- ze msg notyet www.myfunphysicsworld.blogspot.com
  59. 59. www.myfunphysicsworld.blogspot.com
  60. 60. www.myfunphysicsworld.blogspot.com
  61. 61. www.myfunphysicsworld.blogspot.com
  62. 62.  Zero Error = +0.04 mm Correct reading meaning that 0.04 mm Micrometer reading -(+0.04) must be = Micrometer reading - 0.04 substracted from all www.myfunphysicsworld.blogspot.com readings taken.
  63. 63.  Zero Error = -0.03 mm Correct reading meaning that 0.03 mm Micrometer reading - (-0.03) must be = Micrometer reading + 0.03 added to all readings www.myfunphysicsworld.blogspot.com taken.
  64. 64.  Figure shows a micrometer screw gauge used to measure the size of an object. Determine the size of the object if the micrometer has a zero (a) +0.01 mm (b) -0.03 mm www.myfunphysicsworld.blogspot.com
  65. 65.  Solution The reading of the gauge = 4.50 + 0.21 = 4.71 mm (a) Size of object =Reading- Zero Erro = 4.71 – (+0.01) = 4.70 mm (b) Size of object = Reading – Zero Error = 4.71-(-0.03) = 4.74 mm www.myfunphysicsworld.blogspot.com
  66. 66. www.myfunphysicsworld.blogspot.com
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