Part – B (General Studies) (English) NDA/NA SOLVED PAPER 2017 (II) (101 to 150)

Total Questions: 50

1. Which one of the following statements about a satellite orbiting around the Earth is correct?

Correct Answer: (d) Satellite does not required any energy for orbiting.
Solution:

Once a satellite is placed in a stable orbit at the correct speed and altitude, it stays in motion due to inertia and the gravitational pull of the Earth acting as a centripetal force.

According to Newton’s First Law, an object in motion stays in motion unless acted upon by an external force. While energy is needed to launch the satellite, no fuel is consumed to keep it moving in its circular path. Solar panels are used only to power the onboard electronics (cameras, transponders), not for propulsion.

2. Which one of the following statements about energy is correct?

Correct Answer: (c) Energy can neither be created nor destroyed
Solution:

This is the First Law of Thermodynamics. Energy can only be transformed from one form to another (e.g., electrical energy to light energy in a bulb). The total energy of an isolated system remains constant.

3. Step-up transformers are used for:

Correct Answer: (d) increasing voltage
Solution:

A step-up transformer increases the voltage from the primary coil to the secondary coil by having more turns of wire on the secondary side.
Image of step up transformer diagram
It is important to note that while voltage increases, the current decreases proportionally (so that total power P = VI remains roughly the same, minus minor heat losses).

4. Which one among the following waves carries the maximum energy per photon?

Correct Answer: (a) X-rays
Solution:

The energy of a photon is given by the formula E = hf, where h is Planck's constant and f is frequency. X-rays have a much higher frequency (and shorter wavelength) than radio waves, microwaves, or visible light, meaning each X-ray photon carries significantly more energy.

5. How much CO₂ is produced on heating of 1 kg of carbon?

Correct Answer: (a) 11/3Kg
Solution:

The chemical reaction is C + O₂ → CO₂.

  • Atomic mass of Carbon (C) = 12
  • Atomic mass of Oxygen (O) = 16
  • Molecular mass of CO₂ = 12 + (2 × 16) = 44. To find the mass of CO₂ from 1 kg of C:

Mass = (Molecular weight of CO₂ / Atomic weight of C) × 1 kg = 44/12 = 11/3 kg

6. Zinc is used to protect iron form corrosion because zinc is:

Correct Answer: (a) more electropositive than iron
Solution:Zinc is more reactive (more electropositive) than iron. In the process of galvanization, zinc acts as a "sacrificial anode." Even if the zinc coating is scratched, the zinc will corrode/oxidize instead of the iron because it gives up electrons more easily.

7. Which one of the following gases is placed second in respect of abundance in the Earth’s atmosphere?

Correct Answer: (a) Oxygen
Solution:

The Earth's dry atmosphere consists of:

  1. Nitrogen (N₂): ~78%
  2. Oxygen (O₂): ~21%
  3. Argon (Ar): ~0.9%
  4. Carbon Dioxide (CO₂): ~0.04%

8. Which one of the following is a chemical change?

Correct Answer: (b) Graying of hair naturally
Solution:

A chemical change involves the formation of new substances. Natural graying is a biological chemical process where melanin production stops or hydrogen peroxide builds up in the hair follicle. Cutting hair or fruit only changes the physical shape, and resin swelling is a physical absorption of water.

9. Which one among the following chemicals is used as washing soda?

Correct Answer: (c) Sodium carbonate
Solution:

Washing Soda: Sodium carbonate
Baking Soda: Sodium bicarbonate
Limestone: Calcium carbonate

10. Why is potassium permanganate used for purifying drinking water?

Correct Answer: (d) It is an oxidising agent
Solution:

Potassium permanganate is a powerful oxidizing agent. It purifies water by oxidizing dissolved organic matter and iron/manganese, effectively killing bacteria and neutralizing organic contaminants. While it "kills germs" (a), the reason it does so is because of its chemical property as an oxidizer.