A radio set that uses valves does not start operating immediately when it is switched on whereas a set containing only tranaistors operates immediately. The reason for this is that
the valve filaments have low resistance
valve-radio sets work at a higher voltage
transistor set has a low resistance
filaments of the valves cake time to beat up and function
Correct Answer :
D. filaments of the valves cake time to beat up and function
Related Questions
The completely dark portion of a shadow of an object is known as
umbra
penumbra
image
black portion of light
Drinks kept in a vacuum flask remain hot or cold as the case may be for a long time because
both walls are silvered on the vacuum side
there is vacuum between the double walls
the cork is a poor conductor of heat
of all the above
The period of oscillation of a simple pendulum depends upon
the mass of its bob
the material of the bob
the amplitude of vibration
acceleration due to the gravity at the site of experiment
A rod of brass la held in hand and rubbed with fur. The rod is found to have
no charge
positive charge
negative charge
can't be said
Which force is used when milk is churned to separate cream?
cohesive
centrifugal
frictional
gravitational
Solar radiation is preferred to other sources of energy because
it is practically inexhaustible
it is the cheapest form of energy
it does not cause pollution
All of the above
The mirage is a phenomenon
generally considered as a desert happening
caused by unequal heating of the several layers of the atmosphere above the desert
in which the refracted rays take a curved path resulting in total internal refection
All the above
The inside of both the walls of a thermos flask is silvered i.e., on the vacuum side in order to reduce heat loss by
convection
radiation
conduction
All the three
The shadow below a tree has bright spots in it because
light comes through circular gaps between the leaves
the leaves are circular
the rays bend to form circular spots
the gaps between the leaves act as pin holes
Acoustics is a property or
Physics
Chemistry
Biology
Economic
In which of the following will a piece of iron weigh most?
in air
in an atmosphere of oxygen
in an atmosphere of CO2
in vacuum
Hot water is poured simultaneously in four metallic tumblers painted outside with different paints. After some time the water will be found to have cooled most in the tumbler painted.
rough white
rough black
shining white
shining black
A pressure gauge for fluids is called
a hydrometer
a manometer
a lactometer
an anemometer
The number of galaxies that are visible without telescope on clear dark nights and away from bright lights is
one
two
three
infinite
Pieces of camphor placed on water move about rapidly. This is because of
diffusion
viscosity
surface tension
capillarity
A thermostat is a device used
for automatically maintaining a steady temperature
for measuring electricity
to reduce the voltage of electricity
for producing heat
Skating on ice is possible because
the surface of ice is smooth
ice is cold
the pressure on the ice due to skate melts the ice by lowering its melting point forming a thin film of water
the pressure on the ice due to skate raises its melting point
The principle of equivalence of mass and energy was established by
Dalton
Rutherford
Einstein
Planck
The power of a lens is
equal to its focal length
equal to its radius of curvature
equal to the reciprocal of its focal length (in metres)
equal to twice its focal length
Echoes are produced by
the reflection of sound waves
the refraction of sound waves
the interference of sound waves
reverberation of sound waves
In a freezer ice cubes will be formed more quickly in trays made of
rubber
plastic
aluminium
wood
When an incident beam of light strikes the surface of a glass slab normally, the refracted beam
goes straight through without bending
gets deviated away from the normal
gets bent towards the normal
gets reflected
The velocity of sound in air increases with
the rise of temperature
rise of its frequency
decrease in humidity
fall of temperature
Pyrometers are instruments used
for measuring the velocity of wind
in the manufacture of fireworks
in finding the coefficient of apparent expansion of a liquid
for measuring high temperatures
No current will flow between two charged bodies if they have the same
resistance
charge
potential
charge/potential ratio
If a band is played on the moon the sound will
reverberate
be heard by us faintly
be heard upto 10 km from it
not be heard at any distance at all from it
The Space Application Centre for training in Satellite Communication Technology is located at
Bangalore
Mumbai
Ahmedabad
New Delhi
Atoms which have the same atomic number but different mass numbers are called
isobars
isomers
isotones
isotopes
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
In the visible spectrum which colour has the shortest wavelength?
Red
Blue
Yellow
Violet