Signs and Symbols

Ampere :

Unit of electric current. It is approximately equal to the flow of 6.023 x 1023 electrons per second.


Watt :

Unit of power, it is the rate of work done in joules per seconds.


Volt :

It is a unit of potential difference. The difference of potential between two parts on a conducting wire carrying a constant current of 1 ampere when the power dissipated between these two points is 1 watt.


Quintal :

Metric measure of weight; 100 kilograms = 1 quintal.


Pressure :

The pressure is expressed in pounds weight per The pressure of the atmosphere is expressed in millibars. One millibar = 1 dyne per If the pressure is very high, this is expressed in multiple of atmospheric pressure 1 atmosphere is a pressure exerted by a column of mercury, 76 cm . high at sea level and at a latitude of 45.


Knot :

It is a measure to find the speed of a ship.


Light year :

A light year is the distance, light travels in one mean solar year, at a speed of 1,86,000 miles per second. It is equal to 5,880,000,000,000 miles.

It is used as a unit for measuring stellar distances.


Nautical Mile :

A unit of distance used in navigation. A nautical mile is approximately equal to 6,080 feet.


Joule :

It is the unit of work or energy. It is equal to 10 ergs. It is the energy consumed in one second in an electrical circuit through which a current of one ampere is flowing against a potential difference of one volt.


Horse Power :

The practical unit of power, it is the power of an agent which can work at the rate of 550 foot pounds per second or 33,000 foot pounds per minute.

1 HP = 746 watts.


Calories :

It is the unit of heat. It is the amount of heat required to raise the temperature of one gram of water.


Bar :

Bar is the unit of atmospheric pressure; one bar is equal to a pressure of 106 dynes per


Atomic weight :

The weight of an atom of hydrogen is taken as standard. The respective weights of the atoms of all other substances are expressed in terms of it. So, when it is stated that the atomic weight of iron is 56m, it is meant that an atom of iron is 56 times as heavy as an atom of hydrogen.


Angstrom :

The unit of wavelength of light is Angstrom. 1 Angstrom = 10-6 cm.