Physics topic – “Measurement Units (मापन के मात्रक/इकाई)“, is important for all competitive exams like SSC CGL, SSC CHSL, RRB NTPC, UPSC and other state civil services exams. In these exams, almost 4-5 questions are coming from Physics. Let’s start the topic – Measurement Units (मापन के मात्रक/इकाई).
(मापन के मात्रक/इकाई)
Definition of physics: The branch of science concerned with the nature and properties of matter and energy.
- In Number: 1) Octal 2) Decimal 3) Hexadecimal
- In Unit: The word unit as used in physics binary refers to the standard measure of a quantity.
Units: Unit are mainly two types :-
- Basic unit: Total basic unit are 7 ⇒ 6-physics + 1- chemistry
- Derived unit: ∞ (infinity)
- The SI base units are the standard units of measurement defined by the International System of Units(SI) for the seven base quantities.
- I. system starts in 1961 (in jenewa)
- In S.I. system dimensional formula is [M L T] where, M for mass, L for length, T for time.
|Name of the Quantity||SI Unit||SI Unit Symbol|
|Electric current (I)||Ampere||
|Thermodynamic temperature (Θ)||Kelvin||
|Luminous intensity (J) (light)||candela||
|7||Amount of substance (N)||Mole||
This 7th unit is Chemistry unit.
Physical Quantities: – These are those quantities which can be measured accurately.
These are mainly two types:
- Scalar quantity: The physical quantity with magnitude only, no direction. E.g. Mass, Speed etc.
- Vector quantity: A vector is a quantity that has both a magnitude and a direction. For e.g.- force, velocity, acceleration, displacement, and momentum etc.
Some Important Measurement Units of Physics:
1) Light year:–
It is unit of distance through which distance of celestial objects can be measured.
- Distance travelled by light in a year is called One-Light-year.
- Speed of light= 3 x 108 m/sec
- Distance travelled by light in a year = 9.46 x 1012 KM or 9.46 x 1015 meters.
2) Parsec: –
It is largest unit of distance by which distance of celestial (astronomical) object can be measured.
- It is 3.25 times more than the light year.
- 1 parsec = 2.49 x 1013 k.m. or 2.49 x 1016 meters.
3) Astronomical unit: –
It is also the unit of distance by which the distance of celestial (astronomical) object can be measured.
- It is average distance between Sun and Earth.
- 1-astronomical unit = 1.5 x 108 Km or 1.5 x 1011 meters .
4) Fermi unit: –
It is the smallest unit of distance through which atomic radius can be measured.
- It is Atomic distance between molecules.
- 1-Fermi = 10-15 meter
5) Nautical mile: –
This is the unit of distance through which distance in “ocean” as well as “in air” can be measure.
- 1 nautical mile = 1852 meter
6) Naute: –
It is a unit by which the speed of ship can be measured.
- naute = 1852 meter/hours
7) Fathem: –
It is unit by which “Depth of ocean” can be measured.
- Fathem = 6 feet
8) Cusec: –
It is unit through which “flow of liquid” can be determine.
- 1 cusec = feet3 /sec
- 1 cusec = 28 litre
9) Poise: –
It is a unit through which viscosity of liquid can be measured.
- Facts: “clouds” floths in the sky due to less viscosity and low density.
10) Pascal: –
It is unit through which “pressure of gas” can be measured.
- 1 pascal = 1 N/m2
11) Diopter: – It is unit through which “power of lens” can be measure.
12) Richter scale: – Unit through which intensity of earth quack can be measured
13) PH- Scale: – Through which “strength of acid and base” can be measured.
14) Curine/Rutherford/Brequell: – These are units through which “Intensity of Radio activity” can be measured.
15) Decibel:- It is unit through which Intensity of the sound can be measured.
16) Aung strung (Aº):- It is unit through which cellular component like membrane etc. can be measured.
- 1 A º= 10-10 meter
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