Applied physics-1.pptx measurement and error

Measure and error

1. Applied physics-1 Measurement and Errors

2. What is physics फिजिक्स विज्ञान की वह शाखा है जिसमें पदार्थ और उर्जा के प्रकृति और गुणों के बारे में अध्ययन किया जाता है. भौतिक विज्ञान में पदार्थ के रूप में मैकेनिक्स, गर्मी, लाइट, रेडिएशन, साउंड, बिजली, मैग्नेटिज्म और परमाणु की संरचना शामिल है. Physics is the branch of science in which the nature and properties of matter and energy are studied. Physics includes the mechanics, heat, light, radiation, sound, electricity, magnetism and the structure of an atom.

3. Fundamental forces in nature Gravitational Force – Weakest force; but has infinite range. Weak Nuclear Force – Next weakest; but short range. Electromagnetic Force – Stronger, with infinite range. Strong Nuclear Force – Strongest; but short range.

4. Block diagram

5. Physical quantities Quantities that can be measured, and in terms of which, laws of physics are described are called physical quantities. Examples are length, mass, time, force, energy, etc.   Physical quantities are classified into two types. There are fundamental and derived quantities.

6. Types of physical quantities Fundamental or base quantities are quantities which cannot be expressed in terms of any other physical quantities. These are length, mass, time, electric current, temperature, luminous intensity and amount of substance .   Quantities that can be expressed in terms of fundamental quantities are called derived quantities. For example, area, volume, velocity, acceleration, force.  

7. Different types of measurement systems T he f.p.s . system  is the British   Engineering system of units, which uses  foot ,  pound  and  second  as the three   basic units for measuring length, mass and time respectively . The c.g.s system  is the Gaussian   system, which uses  centimeter, gram  and  second  as the three basic units for measuring length, mass and time respectively The m.k.s system  is based on   metre ,   kilogram  and  second  as the three basic   units for measuring length, mass and time respectively . The  SI base units  are the standard  units of measurement  defined by the  International System of Units  (SI) for the seven  base quantities  of what is now known as the  International System of Quantities : 

8. Seven fundamental quantities and their units Serial no. Fundamental quantity unit symbol 1- Length metre m 2- Mass kilogram kg 3- Time Second s 4- Electric current ampere A A Temperature kelvin K 6- Luminous intensity candela Cd 7- Amount of substance mole mol

9. Derived quantities and their units

10. Dimensions of physical quantities Dimensions of a physical quantity are the powers to which the fundamental units are raised to obtain one unit of that quantity. The fundamental physical quantities namely length,mass and time are represented by L,M,and T respectively. Dimensional formula is the formula in which the given physical quantity is expressed in terms of the fundamental quantities raised to suitable powers.

11. Dimension formula for physical quantities

12. Error in measurement The measurement error is defined as the difference between the true or actual value and the measured value . The true value is the average of the infinite number of measurements, and the measured value is the precise value.

13. Types of errors Gross Errors Systematic Errors Random Errors

14. Error block diagram

15. Gross error The gross error occurs because of the human mistakes . For examples consider the person using the instruments takes the wrong reading, or they can record the incorrect data. Such type of error comes under the gross error. The gross error can only be avoided by taking the reading carefully.

16. Systematic errors The systematic errors are mainly classified into three categories. Instrumental Errors Environmental Errors Observational Errors

17. Instrumental errors These errors mainly arise due to the three main reasons. (a) Inherent Shortcomings of Instruments –   Such types of errors are inbuilt in instruments because of their mechanical structure . (b) Misuse of Instrument – The error occurs in the instrument because of the fault of the operator . (c) Loading Effect  – It is the most common type of error which is caused by the instrument in measurement work. For example, when the voltmeter is connected to the high resistance circuit it gives a misleading reading, and when it is connected to the low resistance circuit, it gives the dependable reading. This means the voltmeter has a loading effect on the circuit.

18. Environmental errors These errors are due to the external condition of the measuring devices . Such types of errors mainly occur due to the effect of temperature, pressure, humidity, dust, vibration or because of the magnetic or electrostatic field. 

19. Observational errors Such types of errors are due to the wrong observation of the reading. There are many sources of observational error.

20. Random errors The error which is caused by the sudden change in the atmospheric condition, such type of error is called random error . These types of error remain even after the removal of the systematic error. Hence such type of error is also called residual error.

21. Propagation of errors Error propagation (or  propagation of uncertainty ) is what happens to measurement errors when you use those uncertain measurements to calculate something else . For example, you might use  velocity  to calculate kinetic energy, or you might use length to calculate area. When you use uncertain measurements to calculate something else, they propagate   (grow much more quickly than the sum of the individual errors).

22. Significant figures Every measurement results in a number that includes reliable digits and uncertain digits. Reliable digits plus the first uncertain digit are called significant digits or significant figures.These indicate the precision of measurement which depends on least count of measuring instrument. Example, period of oscillation of a pendulum is 1.62 s. Here 1 and 6 are reliable and 2 is uncertain. Thus, the measured value has three significant figures.

23. Rules for significant figures All non-zero digits are significant. All zeros between two non-zero digits are significant irrespective of decimal place. For a value less than 1, zeroes after decimal and before non-zero digits are not significant. Zero before decimal place in such a number is always insignificant.

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