A permanent magnet may be demagnetised by
placing it inside a solenoid through which an alternating current is flowing
heating the magnet to redness and then allowing it to cool
dropping it several times or hammering it while lying east-west
All the above
Correct Answer :
D. All the above
Related Questions
A piece of cork la embedded inside an ice block which floats in water. What will happen to the level of water when all ice melts?
It will go down
It will come up
It will remain at the same level
First it will go down and it will come up
X-rays are used
in hospital in the treatment of malignant growth
to reveal hidden flaws in metal castings and welded joints
to detect alterations made in works of art
All the above
Electron-volt is a unit of
power
velocity
energy widely used in nuclear physics
number of electrons
The earth satellite Aryabhatta was put in orbit by India on
October 20, 1978
November 14, 1978
January 26, 1979
April 19, 1975
Meteors
look like falling stars
are really pieces of rock or metal
burn up as they shoot through the air
All the above
X-rays are used
in hospital in the treatment of malignant growth
to reveal hidden flaws in metal castings and welded joints
to detect alterations made in works of art
All the above
The enormous energy released in nuclear and thermonuclear reactions is due to conversion of
chemical energy into heat energy
mechanical energy into heat energy
protons into neutrons
mass into energy according to Einstein's equation
For detecting and, testing of small electric charges we use
an electrophorus
an electroscope
an electromagnet
an ammeter
Fish and other aquatic creatures can live inside a deep frozen pond because
fish are cold-blooded animals
ice is a bad conductor of heat
there will always be water just beneath the ice level
they can adapt themselves to live in ice
Nichrome is used in electric heaters and irons because
it resists oxidation when red hot
its melting point is high
it has got 60 times the resistance of copper
All the above
It is difficult to bon potatoes at the top or a mountain because
the water available is hard
it is colder than at sea level
the potatoes become hard
the boiling point of water is lower at that height on account of low atmospheric pressure
The frequency of an ultrasonic wave is
the same as that of an audible sound
above the audible range
below the audible range
None of the above
Out of the following which is an insulator?
Silver
Copper
Nichrome
Dry wood
The attraction of unlike molecules at the common surface is known as
adhesion
cohesion
surface tension
capillarity
The characteristics of a musical note are
loudness
pitch
quality or timbre
All the above
A pressure gauge for fluids is called
a hydrometer
a manometer
a lactometer
an anemometer
The maximum displacement of the particle in a mechanical wave motion is known as
amplitude
vibration
frequency
phase
The heating element often used in an electric iron is
copper
tungsten
mica
nichrome
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
Which mirror is used as a rear view mirror in Vehicles?
Parabolic
Convex
Concave
Plain
Air pressure is usually highest when the air is
warm and moist
cool and dry
warm and dry
cool and moist
Warm air will hold more water vapour than cold air because
it is lighter
it has more water vapour in it
its molecules are close together
its molecules are far apart
The SI unit of electric current is
the ampere
the volt
the ohm
the coulomb
'Acoustics' is a branch or study dealing with
historical sites
architecture
sound
trigonometry
Of the following types of electromagnetic radiation which has the longest wavelength?
ultraviolet rays
gamma rays
radio waves
infrared waves
A car parked in the sun with its windows closed gets terribly hot inside. This is due to
the heat emitted by the engine
the greenhouse effect
the good conducting power of the metal body
the double layered wind shield
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
Moon has no atmosphere because
it has no population
it is quite far off
its surface is full of rocks
its gravity is not sufficient for any atmosphere to hold on to it
On the Kelvin scale, the melting point of ice is
0 K
273 K
373 K
100 K
A workman was working on a rail track. A young boy at a distance holds his ear close to the railway track. The boy was able to hear the sound of each blow or the workman twice. It is because
speed of sound is greater in steel than in air
speed of sound is greater in air than in steel
part of sound waves is reflected between rail tracks
the boy's ears are at a different distance from the source