UPSC – CSE Prelims 2024
DIFFICULT
S&T – SPACE
1. With reference to radioisotope thermoelectric generators (RTGs), consider the following statements:
- RTGs are miniature fission reactors.
- RTGs are used for powering the onboard systems of spacecrafts.
- RTGs can use Plutonium-238, which is a by-product of weapons development.
Which of the statements given above are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Ans. (b)
Radioisotope Thermoelectric Generator (RTG)
- It is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect.
- This type of generator has no moving parts and is ideal for deployment in remote and harsh environments for extended periods with no risk of parts wearing out or malfunctioning.
- RTGs have been used as power sources in satellites, space probes, and uncrewed remote facilities such as a series of lighthouses built by the Soviet Union inside the Arctic Circle.
- RTGs and fission reactors use very different nuclear reactions.
- The first RTG launched into space by the United States was SNAP 3B in 1961 powered by 96 grams of plutonium-238.
- Plutonium-238 is formed in nuclear power reactors from uranium-238 by neutron capture.
DIFFICULT
S&T – SPACE
2. Consider the following statements:
Statement-I: Giant stars live much longer than dwarf stars.
Statement-II : Compared to dwarf stars, giant stars have a greater rate of nuclear reactions.
Which one of the following is correct in respect of the above statements ?
(a) Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
(b) Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
(c) Statement-I is correct, but Statement-II is incorrect
(d) Statement-I is incorrect, but Statement-II is correct
Ans. (d)
Giant stars
- They have a greater rate of the nuclear reactions that light up stars.
- Massive stars also use up the hydrogen fuel in their core faster, despite starting out with much more of it, meaning they live much shorter lives than dwarf stars.
Day 95 PRELIMS 2024 S&T-Space Arrange the following in chronological order of life cycle of stars. 1. Proto-star 2. Main sequence star 3. Red giant 4. White dwarf Select the correct answer using codes given below. (a) 1-2-3-4 (b) 2-1-3-4 (c) 1-2-4-3 (d) 2-1-4-3 Ans. (a) |
UPSC – CSE Prelims 2023
S&T – SPACE
1. Consider the following pairs:
Objects in space: Description
- Cepheid’s: Giant clouds of dust and gas in space
- Nebulae: Stars which brighten and dim periodically
- Pulsars: Neutron stars that are formed when massive stars run out of fuel and collapse
How many of the above pairs are correctly matched?
(a) Only one
(b) Only two
(c) All three
(d) None
Answer: (a) Only one
Cepheid’s: Giant clouds of dust and gas in space: This description is incorrect. Cepheid’s are not giant clouds of dust and gas. Instead, they are a type of variable star that exhibits periodic changes in brightness. Cepheid’s are used as important distance indicators in astronomy.
Nebulae: Stars which brighten and dim periodically: This description is incorrect. Nebulae are not stars that brighten and dim periodically. Nebulae are vast clouds of dust, gas, and plasma in space. They can be regions of star formation or remnants of exploded stars.
Pulsars: Neutron stars that are formed when massive stars run out of fuel and collapse: This description is correct. Pulsars are highly magnetized, rotating neutron stars that emit beams of electromagnetic radiation. They are formed when massive stars undergo supernova explosions and collapse under their own gravitational forces.
S&T – SPACE
2. Which one of the following countries has its own Satellite Navigation System?
(a) Australia
(b) Canada
(c) Israel
(d) Japan
Answer: (d) Japan
Among the given options, Japan has its own Satellite Navigation System known as the Quasi-Zenith Satellite System (QZSS). QZSS is a satellite-based positioning system designed to augment and enhance the Global Positioning System (GPS) in Japan and the Asia-Oceania region. It provides improved positioning, navigation, and timing services.
Australia does not have its own satellite navigation system. It relies on the Global Positioning System (GPS) and other satellite navigation systems for positioning and navigation.
Canada also does not have its own satellite navigation system. It primarily relies on the GPS system for positioning and navigation.
Israel does not have its own satellite navigation system. It primarily uses the GPS system for positioning and navigation.
Therefore, the Answer: is (d) Japan.