2024 GS Paper I, all questions

UPSC Prelims 2024 · GS Paper I

Question 32: Science and Technology

Consider the following statements :

  1. Statement-IGiant stars live much longer than dwarf stars.
  2. Statement-IICompared 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 ?

aBoth Statement-I and Statement-II are correct and Statement-II explains Statement-I
bBoth Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
cStatement-I is correct, but Statement-II is incorrect
dStatement-I is incorrect, but Statement-II is correct

AnswerUPSC’s answer is (d).

Massive (giant) stars burn their nuclear fuel much faster than small dwarf stars, so they live for only millions of years, while dwarfs can last for billions. So Statement-I is wrong. Statement-II is right: a giant star's greater mass means higher core pressure and temperature and a far greater rate of nuclear reactions, which is exactly why it dies sooner. Remember: bigger star, shorter life.

  • I. Giant stars use up their fuel quickly and live far shorter lives than dwarf stars.
  • II. Giant stars have a greater rate of nuclear reactions than dwarf stars.

How you could have got this

If you were sure Statement-I is not correct, only (d) is left: every other option says it is correct.

What you needed to know: Giant stars use up their fuel quickly and live far shorter lives than dwarf stars.

Which options go is worked out from UPSC’s key and the options, not by a model.

Why each option is right or wrong
  • (a) Wrong: Statement-I is incorrect; giant stars have shorter lives.
  • (b) Wrong: Statement-I is incorrect.
  • (c) Wrong: Statement-I is the incorrect one and Statement-II is correct.
  • (d) Right: giant stars live shorter lives, but they do have a greater rate of nuclear reactions.

Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2024, General Studies Paper I, Series A. The paper on upsc.gov.in.