Metals are good conductors of heat because
they contain free electrons
their atoms are relatively far apart
their atoms collide frequently
they have reflecting surfaces
Correct Answer :
A. they contain free electrons
Related Questions
Rays similar to X-rays but of smaller wave length that are given off by radioactive substances are
�± -rays
�² -rays
�³ -rays
Cosmic rays
The aneroid barometer uses
mercury
distilled water
alcohol
does not use any liquid
When white light passes through a glass prism we get a spectrum on the other side of the prism. In the emergent beam the ray which is deviated least is
the violet ray
the red ray
the green ray
the blue ray
Tea pots are highly polished
so that they may reflect thermal radiation from outside and minimise such radiation from them
so that they may absorb all radiation from outside
to make them attractive to look at
because they take high polish
The maximum range of most TV signals is from 121 to 240 km only because
the curvature of earth limits the range of reception
the signals are weak
the signals are absorbed by air
the antennae are not powerful enough
The phenomenon of spontaneous disintegration of certain heavy nuclei is termed
radioactivity
fission
fusion
implosion
The rate of cooling of a hot body depends on
the nature of the radiating surface
area of the radiating surface
temperature difference between the body and the surroundings
All the above
Which physical quantity is measured in watts
power
kinetic energy
momentum
impulse
The Space Application Centre for training in Satellite Communication Technology is located at
Bangalore
Mumbai
Ahmedabad
New Delhi
A small bubble of air deep down in a lake rises up to the top of the lake. The volume of the bubble on coming up will
increase
decrease
will not change
first increase and then decrease
The planet that spins Caster than any other planet is
Saturn
Jupiter
Earth
Mercury
The rocket engine is motivated by jet propulsion which uses the famous
Kepler's Laws
Newtonian Third Law of Motion
Bernoulli's Principle
Law of Relativity
A convex mirror always produces
an erect, virtual image of diminished size
an erect, real image of diminished size
an erect, real image of double size
a virtual image of double size
The largest reserve of radioactive element which can be used in a nuclear reactor has been found in India, The name of the element is
Thorium
Uranium
Plutonium
Radium
The unit of power in SI is
Joule
Newton
Joule/Sec
Erg/Sec
An electric fan converts
electrical energy into heat energy
electrical energy into mechanical energy
mechanical energy into electrical energy
mechanical energy into heat energy
Of the following which has got the highest frequency?
ultraviolet rays
gamma rays
radio waves
infrared waves
In the fuse of an electrical installation blows out
replace the fuse by a thin wire
replace the fuse by a thick copper wire
replace the fuse by a fuse wire of proper rating
replace the fuse by nichrome wire
In a concert hall reverberation is controlled by
reduction of seating capacity in the hall
increase of sound intensity in the hall
lining the walls, with leather panels put on over a layer of sound absorbent glass fibre
by opening the doors and windows of concert hall
A hydraulic brake in an automobile uses
a fluid to transmit the braking force
the force applied by the driver
hydrogen gas and not any liquid
a vacuum brake
The number of electrons in the outer orbits of a nucleus gives
the mass number
atomic number
atomic weight
absolute number
When an electric bulb breaks, there is an explosive sound. That is due to
the chemical reaction between the gases inside the bulb
the compressed gases inside rushing out suddenly
the air outside rushing in to fill the vacuum inside the bulb
None of the above
When we sweat, we feel comfortable under a fan because
the air circulated by the fan is cool
the fan produces convection currents of air
the air circulated by the fan quickens the evaporation of the moisture on our skin
the air takes away the heat from our body
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
SONAR (Sound Navigation Ranging) is
used by warships and military aircraft to locate enemy submarines
used by ships to determine the depth of water beneath them
a detective device that uses sound to locate under - water objects
All the above
On the Kelvin scale, the melting point of ice is
0 K
273 K
373 K
100 K
The pressure of air at high altitude is less than the atmospheric pressure at the sea level. Hence the boning point of water at a hill top
is more than at sea level
is equal to that sea level
is less than at sea level
depends on the surrounding temperature
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 source of electric energy in an artificial satellite is
mininuclear reactor
a dynamo
a thermopile
solar cells
Electromagnets are used in
the telephone ear piece
the telegraph
the electric bell
All the above