General Knowledge (Part – B : english) (NDA/NA SOLVED PAPER 2021-I) (51 to 100)

Total Questions: 50

1. Consider the following statements about Light year:

1. Light year is a unit for measurement of very large distances.
2. Light year is a unit for measurement of very large time intervals.
3. Light year is a unit for measurement of intensity of light.
Which of the statements given above is/are correct?

Correct Answer: (d) 1 only
Solution:The light-year is a measure of distance, representing the total distance that a beam of light travels in a straight line over the course of one year; thus, option (d) is correct.

2. Which one of the following regarding density of water at atmospheric pressure is correct?

Correct Answer: (a) Density of water at 4°C is 1000 kg/m³.
Solution:The density of water at 4°C is 1000 kg/m³.

3. Which of the following pairs of physical phenomenon and the discoverer is/are correctly matched?

List - IList - II
1. James ChadwickPhotoelectric effect
2. Albert EinsteinNeutron
3. Marie CurieRadium

Select the correct answer using the code given below:

Correct Answer: (d) 3 only
Solution:Marie Curie discovered polonium and radium in 1898. In 1903 they won the Nobel Prize for Physics for discovering radioactivity. In 1911 she won the Nobel Prize for Chemistry for isolating pure radium.
By 1920, physicists knew that most of the mass of the atom was located in a nucleus at its center, and that this central core contained protons. In May 1932 James Chadwick announced that the core also contained a new uncharged particle, which he called the neutron.
Albert Einstein is best known for his equation E = mc², which states that energy and mass (matter) are the same thing, just in different forms. He is also known for his discovery of the photoelectric effect, for which he won the Nobel Prize for Physics in 1921.

4. LED (a semi-conductor device) is an abbreviation that stands for

Correct Answer: (c) Light Emitting Diode.
Solution:
  • LED STAND FOR: LIGHT EMITTING DIODE.
  • LEDs began as exciting but expensive electronic components in the sixties, used in handheld calculators and other similar devices.
  • LEDs can now be used for a number of lighting applications and are available across the spectrum of visible, infrared, and ultraviolet light.

5. The statement "friction force is a contact force while magnetic force is a non-contact force" is

Correct Answer: (a) always true.
Solution:
  • Magnetic forces are non-contact forces; they pull or push on objects without touching them. Magnets are only attracted to a few 'magnetic' metals and not all matter.
    Magnets are attracted to and repel other magnet. Non-contact force occurs due to either attraction or repulsion between two objects such that there is no contact between these objects.
    There is no field linked with the contact force. There is always a field linked with non-contact force.
  • Friction is a contact force when two surfaces interact.
    The static friction case is similar for when the two surfaces are stationary relative to each other. In static friction, the frictional force is whatever value it needs to be to prevent sliding up to some maximum value.

6. Which one of the following is the chemical formula of Hypobromous acid ?

Correct Answer: (b) HOBr
Solution:
  • Hypobromous acid is unstable because the bromine molecule is lightly bound and therefore will react quickly.
  • Free available bromine, or free bromine, is HOBr or hypobromous acid.

7. The composition of gases in exosphere is

Correct Answer: (a) Helium and Hydrogen.
Solution:
  • The exosphere layer is mainly composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen and carbon dioxide closer to the exobase.
  • Thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space.
  • At this distance, radiation pressure from sunlight exerts more force on hydrogen atoms than does the pull of Earth's gravity.
  • Below the exosphere, molecules and atoms of atmospheric gases constantly collide with each other.
  • However, the air in the exosphere is so thin that such collisions are very rare.
  • The most abundantly found gas in exosphere is hydrogen with some helium, carbon dioxide, and atomic oxygen near its base

8. Which one of the following is not used as a raw material in the manufacture of glass ?

Correct Answer: (d) Gypsum
Solution:
  • Glass is made from natural and abundant raw materials (sand, soda ash and limestone) that are melted at very high temperature to form a new material glass
  • Alumina is often used in the production of glass products, lending improved strength; it has even been studied for its potential in creating an unbreakable glass
  • In the glass and textile fiberglass manufacturing process, boric oxide functions as both a flux and network former. It significantly lowers melting temperature and inhibits crystallization of the glass, both of which greatly facilitate processing

9. In electrolytic refining of copper, the electrolyte is a solution of

Correct Answer: (b) acidified copper sulphate.
Solution:
  • Electrolytic refining is the process of refining impure metals by using electricity. In this process impure metal is made as the anode and a strip of pure metal is made the cathode. A solution of a soluble salt of the same metal is taken as the electrolyte.
  • In electrolytic refining of copper, the electrolyte is a solution of acidified copper sulphate. The anode is impure copper, whereas the cathode is a strip of pure copper on passing electric current, pure copper is deposited on the cathode.

10. Solder is an alloy of

Correct Answer: (c) Pb and Sn.
Solution:
  • Solder is a metal alloy usually made of tin and lead which is melted using a hot iron.
  • Alloys commonly used for electrical soldering are 60/40 Sn-Pb, which melts at 188°C (370°F), and 63/37 Sn-Pb used principally in electrical/electronic work. This mixture is a eutectic alloy of these metals, which: has the lowest melting point (183°C or 361°F) of all the tin-lead alloys
  • The solder composition, being free of lead and other known toxic metals, has a composition range of 0.5 - 4.0% antimony, 0.5 - 4.0% zinc, 0.1 - 3.0% silver, 0.1 - 2.0% copper and 86.8 - 98.8% tin, is especially adaptable for plumbing applications where solder joints are exposed to potable water.