Utiization Of Electrical Engg. Theory

Lumen:-

•  Lumen  is defined as the amount of luminous flux given out in space represented by one unit of solid angle by a source having an intensity of one candle in all directions.

                             lumen = candle power * solid angle 

total lumens given out by the source of one candle is 4 pi lumens.

Candle power :-

•  candle power is the light falls upon any surface, the phenomenon is called the illumination. it is defined as the number of lumens, falling on the surface per unit area. 
• it is denoted by symbol  E and is measured in lumen per square metre or lux candle.
• if a flux of F lumens falls on a surface of area A then the illumination of that surface is    E= F/A lumens / sq. m or lux 
• bigger unit of illumination is phot. 
• 1 phot =10 ^4  lux 

Metre candle :- 

•  it is also known as lux .
• it is the unit of illumination and is defined as the luminous flux falling per sq. meter on the surface which is everywhere perpendicular to the rays of light from a source of one Candle Power and one meter away from it.  Or it is the illumination produced by a source of one candle power on the inner surface of a sphere of a sphere of one meter radius.  

Centimetre Candle :-

• it is also a unit of illumination and is defined as the luminous flux falling per sq cm on the surface which everywhere is perpendicular to the rays of light from a source of one candle power and one cm away from it 

To be continue........ in next post