The function of a moderator in a nuclear reactor is
to absorb unwanted neutrons
to slow down the fast neutrons to secure more effective hits on other nuclei
to decrease the number of fissile nuclei
to increase the number of fissile nuclei
Correct Answer :
B. to slow down the fast neutrons to secure more effective hits on other nuclei
Related Questions
Which metal is used in storage batteries?
Copper
Lead
Tin
Iron
The asteroids belt lies between the orbits of
Earth and Mars
Venus and Earth
Mars and Jupiter
Moon and Mars
In experiments on static electricity the standard method for obtaining small amounts of positive electricity is to rub
a glass rod with flannel
an abonite rod with flannel
a glass rod with silk
Any of the above
The stem of a vibrating tuning fork is pressed against a sound box. Then
the loudness of the sound increases
the loudness remains the same
the loudness decreases
the sound suddenly stops
Acoustics is a property or
Physics
Chemistry
Biology
Economic
The electrical domestic tube light gives white fiourescent light because of
collision between molecules of filled gas under electric current
heavy current
vacuum inside the tube
falling of ultra violet rays on the white inner coating of the tube
Why is it cool near an open pond on a hot summer day?
Evaporation at the surface causes cooling
The heat obsorbed at the surface is passed on to the bottom
Because of impurity in the water
Because of convection currents set up inside water
The phenomenon of spontaneous disintegration of certain heavy nuclei is termed
radioactivity
fission
fusion
implosion
The light from the star nearest to the sun reaches the earth in
8 minutes
4.3 years
12 seconds
24 hours
A pressure gauge for fluids is called
a hydrometer
a manometer
a lactometer
an anemometer
The plants in a greenhouse are enclosed in a glass enclosure because
glass allows the heat radiations of shorter wavelengths from the sun to pass through
the plants absorb them - these shorter wavelengths - and reradiate them in the form of longer wavelengths
the longer wavelengths cannot penetrate through the glass walls
All the above
A lactometer is used to
find out the specific gravity of liquids
measure the volumes of liquids
test the purity of milk
determine the strength of acid in car batteries
Raindrops assume a spherical shape because or
adhesion
surface tension
gravitational force
atmospheric pressure from all sides
The image formed by a plane mirror is
of the same size as the object
at the same distance behind the mirror as the object is in front of it
virtual and laterally inverted
All the above
Water has maximum density at
0° C
-15° C
4° C
15° C
Gamma radiations are used for
sterilising food stuff
controlling pests
cancer therapy
All of these
When an electric apparatus is fitted with a three core flexible lead the insulation on the three wires is distinctively coloured. The present international convention is
brown for earth, yellow for live, light blue for neutral
green for earth, yellow for live, brown for neutral
yellow for earth, green for live, brown for neutral
brown or red for live, light blue or black for neutral and green or yellow for earth
If a bar magnet is broken into two pieces
both pieces will lose their magnetism
one piece will have North Pole on both ends and the other South Pole on its both ends
each will remain a magnet with North Pole at one end and South Pole at the other
the longer piece will behave as a bar magnet while the smaller will have no magnetism at all
The base of an electric iron is brightly polished mainly
to make it smooth and frictionless
to make it rust - proof
to reduce heat loss by radiation
to make it more durable
A man Jumping out of a moving train is thrown
forward
backward
sideways
None of the above
The stars that shine brightly then dimly and then brightly are known as
meteors
binaries
variable stars
bright stars
A person cups his hand around the mouth when shouting. Why?
Sound energy from his mouth is then directed in one direction
The cupped hand acts as a cardboard tube of short length
The pitch of sound increases
Both (a) and (b)
A lactometer la used to
find out the specific gravity of liquids
measure the volumes of liquids
test the purity of milk
determine the strength of acid in car batteries
Some persons are not able to see distant objects clearly because the image of the object is focused in front of the retina. This defect is known as
short sight
long sight
astigmatism
presbyopia
Mercury does not stick to glass because
cohesive forces between the mercury molecules are greater than adhesive forces between mercury and glass molecules
the adhesive forces between mercury and glass molecules are greater than the cohesive forces
both the cohesive and adhesive forces are equal
None of the above
Cosmic rays contain
protons and electrons
alpha particles
gamma rays
All the above
The distance between two bodies is halved. Now the force of attraction between them will be
half
one fourth
four times
two times
Two tumblers stuck together can be separated by
pouring ice cold water into the inner tumbler
pouring ice cold water on the outer tumbler
pouring hot water into the inner tumbler
dipping both the tumblers in hot water
The audible range of a normal human ear is frequencies ranging from
10000 to 20000 Hz
50 to 15000 Hz
20 to 20000 Hz
15 to 50000 Hz
Chronometer is an instrument to measure
heat
electric potential
time
distance between two points