இந்தக் கட்டுரையில், TNPSC குரூப் 1, குரூப் 2, குரூப் 2A, குரூப் 4 மாநிலப் போட்டித் தேர்வுகளான TNUSRB, TRB, TET, TNEB போன்றவற்றுக்கான முறைகள் இலவசக் குறிப்புகளைப் பெறுவீர்கள்.தேர்வுக்கு தயாராவோர் இங்குள்ள பாடக்குறிப்புகளை படித்து பயன்பெற வாழ்த்துகிறோம்.
ERRORS
The result obtained from any measurement will contain some uncertainty. Such an uncertainty is
termed error.
Errors in Measurement:
The uncertainty in a measurement is called an error. Random error, systematic error and gross
error are the three possible errors.
i) Systematic errors:
Systematic errors are reproducible inaccuracies that are consistently in the same direction. These
occur often due to a problem that persists throughout the experiment. Systematic errors can be
classified as follows
1) Instrumental errors:
When an instrument is not calibrated properly at the time of manufacture, instrumental errors
may arise. If a measurement is made with a meter scale whose end is worn out, the result
obtained will have errors. These errors can be corrected by choosing the instrument carefully.
2) Imperfections in experimental technique or procedure:
These errors arise due to the limitations in the experimental arrangement. As an example, while
performing experiments with a calorimeter, if there is no proper insulation, there will be
radiation losses. This results in errors and to overcome these, necessary correction has to be
applied.
3) Personal errors:
These errors are due to individuals performing the experiment, may be due to incorrect initial
setting up of the experiment or carelessness of the individual making the observation due to
improper precautions.
4) Errors due to external causes:
The change in the external conditions during an experiment can cause error in measurement. For
example, changes in temperature, humidity, or pressure during measurements may affect the
result of the measurement.
5) Least count error:
Least count is the smallest value that can be measured by the measuring instrument, and the error
due to this measurement is least count error. The instrument’s resolution hence is the cause of
this error. Least count error can be reduced by using a high precision instrument for the
measurement.
ii) Random errors:
Random errors may arise due to random and unpredictable variations in experimental conditions
like pressure, temperature, voltage supply etc. Errors may also be due to personal errors by the
observer who performs the experiment. Random errors are sometimes called “chance error”.
When different readings are obtained by a person every time he repeats the experiment, personal
error occurs.
iii) Gross Error:
The error caused due to the shear carelessness of an observer is called gross error.
For example
1. Reading an instrument without setting it properly.
2. Taking observations in a wrong manner without bothering about the sources of errors and
the precautions.
3. Recording wrong observations.
4. Using wrong values of the observations in calculations.
These errors can be minimized only when an observer is careful and mentally alert.
Dimensional analysis:
In mechanics, we deal with the physical quantities like mass, time, length, velocity, acceleration,
etc. which can be expressed in terms of three independent base quantities such as M, L and T.
So, the dimension of a physical quantity can be defined as ‘any physical quantity which is
expressed in terms of base quantities whose exponent (power) represents the dimension of the
physical quantity’.
Length = M 0 LT 0 = L
Area = M 0 L 2 T 0 = L 2
Thus obesity = M 0 L 3 T 0 = L 3
Important facts:
The supplementary quantities of plane and solid angle were converted into Derived
quantities in 1995 (GCWM)
Fermi = 1 fm = 10 −15 m
1 angstrom = 1 Å = 10 −10 m
1 nanometer = 1 nm = 10 −9 m
1 micron = 1μm = 10 −6 m
1 Light year (Distance travelled by light in vacuum in one year) 1 Light Year = 9.467 ×
10 15 m
1 astronomical unit (the mean distance of the Earth from the Sun) 1 AU = 1.496 × 10 11 m
1 parsec (Parallactic second) (Distance at which an arc of length 1 AU subtends an angle
of 1 second of arc) 1 parsec = 3.08 × 10 16 m =3.26 light year
Chandrasekhar Limit (CSL) is the largest practical unit of mass.1 CSL = 1.4 times the
mass of the Sun.
The smallest practical unit of time is Shake.1 Shake = 10 −8 s
In India, the National Physical Laboratory (New Delhi) has the responsibility of
maintenance and improvement of physical standards of length, mass, time, etc.
Matter:
Matter can be defined as anything which has definite masses and occupies space.
Solids:
In solids, atoms or molecules are tightly fixed. In the solid formation, atoms get bound together
through various types of bonding. Due to the interaction between the atoms, they position
themselves at a particular inter atomic distance. This position of atoms in this bound condition is
called their mean positions.
Liquids:
When the solid is not given any external energy such as heat, it will remain as a solid due to the
bonding between atoms. When heated, atoms of the solid receive thermal energy and vibrate
about their mean positions. When the solid is heated above its melting point, the heat energy will
break the bonding between atoms and eventually the atoms receive enough energy and wander
around. Here also the intermolecular (or inter atomic) forces are important, but the molecules
will have enough energy to move around, which makes the structure mobile.
Gases:
When a liquid is heated at constant pressure to its boiling point or when the pressure is reduced
at a constant temperature it will convert to a gas. This process of a liquid changing to a gas is
called evaporation. The gas molecules have either very weak bonds or no bonds at all. This
enables them to move freely and quickly. Hence, the gas will conform to the shape of its
container and also will expand to fill the container.
Plasma:
Super heated form of matter. A major part of the atomic matter of the universe is hot plasma in
the form of rarefied interstellar medium and dense stars.
Bose-Einstein condensates:
Super cooled form of matter.Discoverd with the combined effort of Sathyadranath Bose and
Einstein
Hook’s Law:
The stress is proportional to the strain in the elastic limit.
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