16
|
Describe the advantages
of providing lighting voltage transformer for lighting distribution system.
|
The following are the advantages of providing
lighting voltage transformer for lighting distribution
·
Increase
the life of lamps due to better voltage regulation
·
Increase
the efficiency of lighting system
|
|
17
|
Describe the advantages of Sodium vapour lamp as compare to Mercury
vapour lamp for street lighting.
|
Advantages
of Sodium vapour lamp over Mercury vapour lamp
·
A 150
watt sodium vapour lamp produces approx 15000 lumen whereas 250 watt mercury
lamp produces approx 12700 lumen therefore sodium vapour lamp consume less
energy and produces more lumen output.
·
The life
of the 150 watt sodium vapour lamp is 12000 hours whereas the life of 250
watt mercury lamp is only 5000 hours.
·
The CRI
( colour rendering index ) in the sodium vapour lamp is not as good as that
of mercury vapour lamp(disadvantage)
|
|
18
|
Write the relation between angstrom and Milli - meter
|
One angstrom = 10-10 mm
|
|
19
|
Explain the term : Radiant efficiency
|
Radiant
efficiency
·
When a
current passes through conductor, the radiant energy in the form of heat at
low temperature.
·
The
radiant energy in the form of heat as well as light at high temperature.
·
The
radiant efficiency is the ratio of energy radiated in the form of light to
the total energy radiated from the body.
·
Radiant
efficiency =
Energy
radiated in form of light / Total energy radiated from body
|
|
20
|
Describe the difference between plane angle and solid angle
|
Plane
angle
·
It is
defined as the ratio of length of arc to the radius
Plane
angle = Length of arc / arc radius
Solid
angle
·
It is
defined as the ratio of area of the spherical surface to the square of its
radius.
Solid
angle = Area of sphere / (radius)2
|
|
21
|
How the luminous flux emitted by the light source is determined?
|
Polar curves
|
|
22
|
What is meaning of the Polar curves?
|
Polar
curves
·
It is
drawn by taking luminous intensity by the light source in various directions
at an equal angular displacement in the sphere.
·
It is
plotted between candle power and angular position.
|
|
23
|
Describe the various types of polar curves.
|
Types of
polar curves
·
Vertical
polar curve
·
Horizontal
polar curve
|
|
24
|
Describe the function of the Photometry.
|
Function
of photometry
·
The
function of the photometry is to measure the candle power or luminous
intensity of a given light source.
|
|
25
|
Describe the operating principle of the arc lamps.
|
Principle
of arc lamps
·
The arc
lamp consists of two electrodes which are separated by some distance apart.
·
When a DC supply is given to these
electrodes, current flow through them.
·
The discharge between two electrodes occurs
in the atmosphere. The arc between two electrodes is a source of light.
|
|
26
|
Describe the different types of arc lamps.
|
Types of
arc lamps
·
Carbon
arc lamp
·
Magnetic
arc lamp
·
Flame
arc lamp
|
|
27
|
Whether the size of the positive electrode and negative electrode
should be same in the carbon arc lamp? Why?
|
Size of
electrodes
·
The
diameter of the positive electrode is approximately twice to that of negative
electrode when it is operated on DC supply because the carbon particles
transfer from positive electrode to negative electrode therefore the positive
electrode consumed earlier than the negative electrode.
·
The size
of positive and negative electrodes is same when the carbon arc lamp operated
on alternating supply.
|
|
28
|
Whether the positive and negative electrode emits same light in the
carbon arc lamp when it is operated on DC supply?
|
The positive electrode emits about 85% of light,
negative electrode emits 10% of light and 5% light is given out by the air.
|
|
29
|
Describe the operating principle of the Incandescent lamp.
|
Principle
of incandescent lamp
·
The
incandescent lamp consists of fine metallic wire. When a current passes
through it, it produces heat energy at low temperature. The incandescent lamp
produces light energy and heat energy at high temperature.
|
|
30
|
Describe the properties of the filament material for incandescent lamp.
|
Properties
of filament material
·
High
melting point
·
Low
temperature co – efficient
·
High
resistivity
·
High
mechanical strength to withstand against vibration
·
Ductile
|
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