Part – B (General Studies) NDA/NA SOLVED PAPER 2018 (I) (101 to 150)

Total Questions: 50

1. Which of the following statements about specific heat of a body is/are correct?

1. It depends upon mass and shape of the body
2. It is independent of mass and shape of the body
3. It depends only upon the temperature of the body
Select the correct answer using the codes given below

Correct Answer: (a) 1 only
Solution:

Every substance has a unique value for the amount of heat absorbed or rejected to change the temperature of unit mass of it by one unit. This quantity is referred as the specific heat capacity of a body.
It depends on the nature as well as mass of the substance and its change in temperature. Hence, option (a) is correct.

2. Which one of the, following is an example of the force of gravity of the earth acting on a vibrating pendulum bob?

Correct Answer: (c) Restoring force
Solution:

An object that is vibrating is acted upon by a restoring force. The restoring force causes the vibrating object to slow down as it moves away from the equilibrium position and to speed up as it approaches the equilibrium position.
There is the force of gravity that acts downward upon the bob. And the tension force results from string pulling upon the bob of the pendulum.

3. Which one of the following statements about the refractive index of a material medium with respect to air is correct?

Correct Answer: (d) It is always greater than one
Solution:

Refractive index of a material is given by the ratio of speed of light in vacuum to the speed of light in any medium.
Refractive index is always greater than one because by the definition of refractive index, n of a medium (e.g. glass) is the ratio of the speed of light in a vacuum C, to the speed in the medium v and speed of light is maximum in vaccum, which gives the value of n greater than one.

4. Which one of the following statements about magnetic field lines is NOT correct?

Correct Answer: (c) Field lines between. two poles cannot be precisely straight lines at the ends
Solution:The magnetic field lines is defined as the path along which the compass needless are aligned. They cannot intersect i.e., do not cross each other. Tangent drawn at any point gives the direction of magnetic field.
Outside a magnet, they are directed from north to south pole and inside a magnet they are directed from south to north. These lines are always normal to the surface, which are precisely straight at the ends.
Hence, statement (c) is not correct.

5. Two convex lenses with power 2 dioptre are kept in contact with each other. The focal length of the combined lens system is:

Correct Answer: (d) 0·25m
Solution:

6. Which one of the following alkali metals has lowest melting point?

Correct Answer: (d) Caesium
Solution:

The melting point of alkali metals decreases on moving down the group due to decrease in the extent of metallic bonding. Thus, the sequence of melting point among the given options is
Na > K > Rb > Cs
Therefore, Caesium (Cs) have the least melting point.

7. Which one of the following metals is alloyed with sodium to transfer heat in a nuclear reactor?

Correct Answer: (a) Potassium
Solution:

Sodium-potassium alloy (NaK) is an alloy of two alkali metals sodium and potassium. It is used as a heat-transfer.
Coolant in fast-breeder nuclear reactors and experimentally in gas-turbine power plants.

8. Which one of the following metals is used in the filaments of photo-electric cells that convert light energy into electric energy?

Correct Answer: (a) Tungsten
Solution:

Photo electric cells is a device which convert light-energy directly into electric energy. Main type of these cells are photo voltaic cell, photo emissive cell, photo conductive cell.
The filament of photo electric cells are made up of tungsten. Electrons are obtained from the filament by thermionic emission and are accelerated to the anode by a potential difference (~ 100 kV).

9. Which of the following statements about Ring of Fire is/are correct?

1. It is a zone of convergence plate boundaries
2. It is an active seismic and volcanic zone
3. It is associated with deep trench
Select the correct answer using the codes given below

Correct Answer: (d) 1, 2 and 3
Solution:

The Ring of Fire is a ring of volcanoes around the Pacific Ocean that result from subduction of oceanic plates beneath lighter continental plates. This is also where the Earth’s deep ocean trenches are and where the Earth’s deep earthquakes are.
The trenches form because the downgoing plate is bent downward as it subducts. It is the zone of convergence plate boundaries.

10. Which one of the following Himalayan vegetation species is found between the altitudes of 1800 to 2600 metres?

Correct Answer: (d) Deodar
Solution:

Deodar tree is also known as Himalayan Cedar. These evergreen coniferous trees are native of Pakistan and Himalayas as they thrive at altitudes of 1,500-3,200 meters above sea level.
Deodar grows to a height of 40–60 meters (131–164 feet) with a trunk diameter of 3 meters (10 feet). The timber of Deodar tree is used as construction material for its durability.