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CBSE Notes Class 11 Physics Measurement

by aglasem
June 1, 2022
in 11th Class
MAHE(MET) Applications 2023 - Apply Now!

Class 11 Physics Measurement – Get here the Notes for Class 11 Physics Measurement. Candidates who are ambitious to qualify the Class 11 with good score can check this article for Notes. This is possible only when you have the best CBSE Class 11 Physics study material and a smart preparation plan. To assist you with that, we are here with notes. Hope these notes will helps you understand the important topics and remember the key points for exam point of view. Below we provided the Notes of Class 11 Physics for topic Measurement.

  • Class: 11th
  • Subject: Physics
  • Topic: Measurement
  • Resource: Notes

CBSE Notes Class 11 Physics Measurement

Candidates who are pursuing in Class 11 are advised to revise the notes from this post. With the help of Notes, candidates can plan their Strategy for particular weaker section of the subject and study hard. So, go ahead and check the Important Notes for Class 11 Physics Measurement from this article.

The comparison of any physical quantity with its standard unit is called measurement.

Physical Quantities

All the quantities in terms of which laws of physics are described, and whose measurement is necessary are called physical quantities.

Units

  • A definite amount of a physical quantity is taken as its standard unit.
  • The standard unit should be easily reproducible, internationally accepted.

Fundamental Units

Those physical quantities which are independent to each other are called fundamental quantities and their units are called fundamental units.

S.No.Fundamental QuantitiesFundamental Units Symbol
1.Lengthmetrem
2.Masskilogramkg
3.TimesecondS
4.Temperaturekelvinkg
5Electric currentampereA
6Luminous intensitycandelacd
7Amount of substancemolemol

Supplementary Fundamental Units

Radian and steradian are two supplementary fundamental units. It measures plane angle and solid angle respectively.

S.No.Supplementary Fundamental QuantitiesSupplementary UnitSymbol
1Plane angleradianrad
2Solid anglesteradianSr

Derived Units

Those physical quantities which are derived from fundamental quantities are called derived quantities and their units are called derived units.
e.g., velocity, acceleration, force, work etc.

Definitions of Fundamental Units

The seven fundamental units of SI have been defined as under.

  1. 1 kilogram A cylindrical prototype mass made of platinum and iridium alloys of height 39 mm and diameter 39 mm. It is mass of 5.0188 x 1025 atoms of carbon-12.
  2. 1 metre 1 metre is the distance that contains 1650763.73 wavelength of orange-red light of Kr-86.
  3. 1 second 1 second is the time in which cesium atom vibrates 9192631770 times in an atomic clock.
  4. 1 kelvin 1 kelvin is the (1/273.16) part of the thermodynamics temperature of the triple point of water.
  5. 1 candela 1 candela is (1/60) luminous intensity of an ideal source by an area of cm’ when source is at melting point of platinum (1760°C).
  6. 1 ampere 1 ampere is the electric current which it maintained in two straight parallel conductor of infinite length and of negligible cross-section area placed one metre apart in vacuum will produce between them a force 2 x 10-7 N per metre length.
  7. 1 mole 1 mole is the amount of substance of a system which contains a many elementary entities (may be atoms, molecules, ions, electrons or group of particles, as this and atoms in 0.012 kg of carbon isotope 6C12.

Systems of Units

A system of units is the complete set of units, both fundamental and derived, for all kinds of physical quantities. The common system of units which is used in mechanics are given below:

  1. CGS System In this system, the unit of length is centimetre, the unit of mass is gram and the unit of time is second.
  2. FPS System In this system, the unit of length is foot, the unit of mass is pound and the unit of time is second.
  3. MKS System In this system, the unit of length is metre, the unit of mass is kilogram and the unit of time is second.
  4. SI System This system contain seven fundamental units and two supplementary fundamental units.

Relationship between Some Mechanical SI Unit and Commonly Used Units

S.No.Physical Quantity Unit
1Length(a)1 micrometre = 10-6 m
(b)1 angstrom =10-10 m
2Mass(a)1 metric ton = 103 kg
(b)1 pound = 0.4537 kg
(c)1 amu = 1.66 x10-23 kg
3Volume 1 litre = 10-32 m3
4.Force(a)1 dyne = 10-5 N
(b)1 kgf = 9.81 N
5.Pressure(a)1 kgfm2 = 9.81Nm-2
(b)1 mm of Hg = 133 Nm-2
(c)1 pascal = 1 Nm-2
(d)1 atmosphere pressure = 76 cm of Hg = 1.01 x 105 pascal
6.Work and energy(a)1 erg =10-7 J
(b)1 kgf-m = 9.81 J
(c)1 kWh = 3.6 x 106 J
(d)1 eV = 1.6 x 10-19 J
7.Power(d)1 kgf- ms-1 = 9.81W
 1 horse power = 746 W

Some Practical Units

  1. 1 fermi =10-15 m
  2. 1 X-ray unit = 10-13 m
  3. 1 astronomical unit = 1.49 x 1011 m (average distance between sun and earth)
  4. 1 light year = 9.46 x 1015 m
  5. 1 parsec = 3.08 x 1016 m = 3.26 light year

Some Approximate Masses

ObjectKilogram
Our galaxy2 x 1041
Sun2 x 1030
Moon7 x 1022
Asteroid Eros5 x 1015

Dimensions

Dimensions of any physical quantity are those powers which are raised on fundamental units to express its unit. The expression which shows how and which of the base quantities represent the dimensions of a physical quantity, is called the dimensional formula.

Dimensional Formula of Some Physical Quantities

S.No. Physical Quantity Dimensional Formula MKS Unit
 1Area[L2]metre2
 2Volume[L3]metre3
 3Velocity[LT-1]ms-1
 4Acceleration[LT-2]ms-2
 5Force[MLT-2]newton (N)
 6Work or energy[ML2T-2]joule (J)
 7Power[ML2T-3]J s-1 or watt
 8Pressure or stress[ML-1T-2]Nm-2
 9Linear momentum or Impulse[MLT-1]kg ms-1
 10Density[ML-3]kg m-3
 11StrainDimensionlessUnitless
 12Modulus of elasticity[ML-1T-2]Nm-2
 13Surface tension[MT-2]Nm-1
 14Velocity gradientT-1second-1
 15Coefficient of velocity[ML-1T-1]kg m-1s-1
 16Gravitational constant[M-1L3T-2]Nm2/kg2
 17Moment of inertia[ML2]kg m2
 18Angular velocity[T-1]rad/s
 19Angular acceleration[T-2]rad/S2
20Angular momentum[ML2T-1]kg m2S-1
21Specific heatL2T-2θ-1kcal kg-1K-1
22Latent heat[L2T-2]kcal/kg
23Planck’s constantML2T-1J-s
24Universal gas constant[ML2T-2θ-1]J/mol-K

Homogeneity Principle

If the dimensions of left hand side of an equation are equal to the dimensions of right hand side of the equation, then the equation is dimensionally correct. This is known as homogeneity principle.

Mathematically [LHS] = [RHS]

Applications of Dimensions

  1. To check the accuracy of physical equations.
  2. To change a physical quantity from one system of units to another system of units.
  3. To obtain a relation between different physical quantities.

Significant Figures

In the measured value of a physical quantity, the number of digits about the correctness of which we are sure plus the next doubtful digit, are called the significant figures.

Rules for Finding Significant Figures

  1. All non-zeros digits are significant figures, e.g., 4362 m has 4 significant figures.
  2. All zeros occuring between non-zero digits are significant figures, e.g., 1005 has 4 significant figures.
  3. All zeros to the right of the last non-zero digit are not significant, e.g., 6250 has only 3 significant figures.
  4. In a digit less than one, all zeros to the right of the decimal point and to the left of a non-zero digit are not significant, e.g., 0.00325 has only 3 significant figures.
  5. All zeros to the right of a non-zero digit in the decimal part are significant, e.g., 1.4750 has 5 significant figures.

Significant Figures in Algebric Operations

(i) In Addition or Subtraction In addition or subtraction of the numerical values the final result should retain the least decimal place as in the various numerical values. e.g.,

If l1= 4.326 m and l2 = 1.50 m

Then, l1 + l2 = (4.326 + 1.50) m = 5.826 m

As l2 has measured upto two decimal places, therefore

l1 + l2 = 5.83 m

(ii) In Multiplication or Division In multiplication or division of the numerical values, the final result should retain the least significant figures as the various numerical values. e.g., If length 1= 12.5 m and breadth b = 4.125 m.

Then, area A = l x b = 12.5 x 4.125 = 51.5625 m2

As l has only 3 significant figures, therefore

A= 51.6 m2

Rules of Rounding Off Significant Figures

  1. If the digit to be dropped is less than 5, then the preceding digit is left unchanged. e.g., 1.54 is rounded off to 1.5.
  2. If the digit to be dropped is greater than 5, then the preceding digit is raised by one. e.g., 2.49 is rounded off to 2.5.
  3. If the digit to be dropped is 5 followed by digit other than zero, then the preceding digit is raised by one. e.g., 3.55 is rounded off to 3.6.
  4. If the digit to be dropped is 5 or 5 followed by zeros, then the preceding digit is raised by one, if it is odd and left unchanged if it is even. e.g., 3.750 is rounded off to 3.8 and 4.650 is rounded off to 4.6.

Error

The lack in accuracy in the measurement due to the limit of accuracy of the instrument or due to any other cause is called an error.

1. Absolute Error

The difference between the true value and the measured value of a quantity is called absolute error.

If a1 , a2, a3 ,…, an are the measured values of any quantity a in an experiment performed n times, then the arithmetic mean of these values is called the true value (am) of the quantity.

CBSE Class 11 Physics Notes : Measurement

The absolute error in measured values is given by

Δa1 = am – a1
Δa2 = am – a1

………….

Δam = Δam – Δan

2. Mean Absolute Error

The arithmetic mean of the magnitude of absolute errors in all the measurement is called mean absolute error.

CBSE Class 11 Physics Notes : Measurement

3. Relative Error The ratio of mean absolute error to the true value is called relative

CBSE Class 11 Physics Notes : Measurement

4. Percentage Error The relative error expressed in percentage is called percentage error.

CBSE Class 11 Physics Notes : Measurement

Propagation of Error

(i) Error in Addition or Subtraction Let x = a + b or x = a – b

If the measured values of two quantities a and b are (a ± Δa and (b ± Δb), then maximum absolute error in their addition or subtraction.

Δx = ±(Δa + Δb)

(ii) Error in Multiplication or Division Let x = a x b or x = (a/b).
If the measured values of a and b are (a ± Δa) and (b ± Δb), then maximum relative error

CBSE Class 11 Physics Notes : Measurement

Class 11 Key Points, Important Questions & Practice Papers

Hope these notes helped you in your schools exam preparation. Candidates can also check out the Key Points, Important Questions & Practice Papers for various Subjects for Class 11 in both Hindi and English language form the link below.

Class 11 Physics कक्षा 11 अर्थशास्त्र
Class 11 Chemistry कक्षा 11 समाज शास्त्र
Class 11 Maths कक्षा 11 शारीरिक शिक्षा
Class 11 Biology कक्षा 11 राजनीति विज्ञान
Class 11 Business Studies कक्षा 11 इतिहास
Class 11 Accountancy कक्षा 11 भूगोल 
Class 11 Sociology 
Class 11 Physical Education 
Class 11 English 

 Class 11 NCERT Solutions

Candidates who are studying in Class 11 can also check Class 11 NCERT Solutions from here. This will help the candidates to know the solutions for all subjects covered in Class 11th. Candidates can click on the subject wise link to get the same. Class 11 Chapter-wise, detailed solutions to the questions of the NCERT textbooks are provided with the objective of helping students compare their answers with the sample answers.

  • Biology
  • Chemistry
  • Physics
  • Mathematics
  • English
  • Hindi
  • Business Studies

Class 11 Mock Test / Practice

Mock test are the practice test or you can say the blue print of the main exam. Before appearing in the main examination, candidates must try mock test as it helps the students learn from their mistakes. With the help of Class 11 Mock Test / Practice, candidates can also get an idea about the pattern and marking scheme of that examination. For the sake of the candidates we are providing Class 11 Mock Test / Practice links below.

  • Maths
  • Physics
  • Chemistry
  • Biology

 Class 11 Exemplar Questions

Exemplar Questions Class 11 is a very important resource for students preparing for the Examination. Here we have provided Exemplar Problems Solutions along with NCERT Exemplar Problems Class 11. Question from very important topics is covered by Exemplar Questions for Class 11.

Physics रसायन विज्ञान
Chemistry जीव विज्ञान
Maths
Biology

CBSE Notes for Class 11 Physics Notes Biology Notes Maths Notes Chemistry Notes

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