UPSC Prelims 2003 · General Studies
Question 8: Science and Technology
A hydrogen-inflated polythene balloon is released from the surface of the earth. As the balloon rises to an altitude up in the atmosphere, it will
AnswerThe answer is (c).
Air pressure falls steadily with altitude, so the pressure outside the balloon drops while the hydrogen inside is still at its release pressure. The gas expands (Boyle's law: pressure times volume stays roughly constant at constant temperature) and the balloon grows larger until the polythene eventually bursts. Remember: lower outside pressure, bigger balloon.
Why each option is right or wrong
- (a) Lower outside pressure makes the gas expand, not shrink.
- (b) Nothing squeezes the balloon unevenly; falling pressure expands it in all directions.
- (c) Correct: the balloon increases in size.
- (d) Its size changes because the outside pressure falls with height.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2003, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.