KERALA PSC / PHYSICS / UNITS AND MEASUREMENTS / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

 

KERALA PSC / PHYSICS / UNITS AND MEASUREMENTS / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

KERALA PSC / PHYSICS / UNITS AND MEASUREMENTS / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

·      The unit of physical quantity is defined as the reference standard used to measure it.

·      Fundamental units are the units of fundamental quantities

·      Magnitude of a physical quantity is the product of units in which the quantity is measured and the number of times that unit is contained in the given quantity.

·      Seven fundamental units are metre, kilogram, second, ampere, kelvin, candela, mole

·      CGS system based upon basic units such as centimeter gram, and second

·      FPS system based upon three basic units such as foot pound and second.

·      Light Year: It is the distance travelled by light at a speed 3 ×10⁸ ms־¹

·      It may also be defined as the distance travelled by light in vacuum in one year

1 light year = 3 ×10⁸ ms־¹ ×365 ¼ years = 9.5 ×10¹⁵m

·      Astronomical Units: It is the mean distance of the sun and earth.

1 Au = 1.496 × 10¹¹m

1 par sec (parallactic second) = 3.26 light year or 3.08 ×10¹⁶ m

1 par sec > 1 light year > 1 Au

1 Micron (1 µ m) - 10־⁶ m (used commonly in biology)

1 nanometre (1 nm) - 10־⁹ (used by optical designers)

1 angstrons (1A⁰) - 10־¹⁰ m

Chandra sekhar Limit

1 CSL 1.4 times mass of sun = 2.8 ×10³¹kg

·      The purest form of gold is 24 carats. Ornaments are usually made of 22 carat gold. One metric carat is equal to 200 milligram.

·      The weight of precious gems is also measured in carat

·      One gallon is equal to 4.546 litres

·      One horse power is equal to 746 watts.

·      Light year is a unit of distance used in astronomy

·      Light year is the distance that light travels in one year at the speed of 300000 km/sec.

·      Astronomical Unit is another unit of distance in space. It is the mean distance between earth and Sun. One light year contains nearly 63282 Astronomical Units

·      Par sec (Parallactic second) is yet another unit of distance in space. One par second is equal to 3.08 ×10¹⁶m.

·      Lambert is the unit of intensity of light

·      Pascal is the unit of pressure

·      Angstrom is the unit of the wave length of light

·      Poise is the unit of viscosity of fluid

·      Curie and Rutherford are unit of radio activity.

·      Unit of Plane angle is radian

·      Unit of solid angle is steradian

·      Newton is the unit of force

·      Joule is the unit of energy and work

·      Unit of power is watt

·      Hertz is the unit of frequency

·      Coulomb is the unit of electric charge

·      Unit of electric capacitance is farad

·      Ohm is the unit of electric resistance

·      Becquerel is the unit of radio activity

·      Henry is the unit of inductance

·      Weber is the unit of magnetic flux

·      Lumen is the unit of luminous flux

·      Lux is the unit of illuminance

·      Unit of electric conductance is Siemens

·      Joule is the unit of work

·      Dyne is the unit of force

·      Newton is yet another unit of force

·      One Newton = 10⁵ dynes

·      Centigrade, Fahrenheit are the units of temperature

·      Degree is the unit of angle

·      Mho is the unit of conductance

·      Fathom is the unit of depth of the sea. One fathom is equal to 6 feet

·      In India, National Physical Laboratory of New Delhi is responsible for the maintenance and improvement of physical standards of length and time

·      Solar day is the period between noons of two consecutive days.

KERALA PSC / PHYSICS / UNITS AND MEASUREMENTS / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES