1741. Under normal conditions , the velocity of sound in the air is _____.

A. 33 m/sec
B. 300 m/sec *
C. 600 m/sec
D. 3,300 m/sec

1742. What is the melting point of Tungsten?

A. 500 Degree centigrade
B. 1,000 Degree centigrade
C. 2,000 Degree centigrade
D. 3,000 Degree centigrade *

1743. Which of the following are emitted by the filament of a vaccum tube?

A. Electrons *
B. Neutrons
C. Protons
D. All of these

1744. The transformer works on which of the following principles?

A. Electro-magnetic attraction
B. Electro-magnetic repulsion
C. Electro-magnetic induction *
D. Electro-magnetic conduction

1745. What is the mass of a positron?

A. Equivalent to a neutron
B. Equivalent to a proton
C. Equivalent to the sum of a neutron and an electron
D. Equivalent to an electron *

1746. Which of the following is used as an electrolyte in chromium -plating?

A. Chromium solution in mercury
B. Chromic acid solution *
C. Solution of oxide of chromium in water
D. All of these

1747. What is the number of basic units in the international system of units?

A. 4
B. 5
C. 6
D. 7 *

1748. Why does a stick partly immersed in water appear to be broken at the junction of water and air? This is due to _______.

A. Scattering of light
B. Reflection of light
C. Refraction of light *
D. Both A and B above

1749. Why does the mercury column in the barometer fall rapidly before a severe storm?

A. It is due to increase in humidity in air
B. It is because of the rising pressure in the air.
C. It is due to the fall in atmospheric pressure *
D. It is due to severe heat energy from the sun

1750. Why is it easier to swim sea water than in river?

A. Currents in sea water keeps the person afloat
B. Sea water is saltish and so has an upward thrust
C. Density of sea water is higher *
D. None of these