UPSC Prelims 2015 · GS Paper I
Question 95: Science and Technology
With reference to 'fuel cells' in which hydrogen-rich fuel and oxygen are used to generate electricity, consider the following statements :
- 1.If pure hydrogen is used as a fuel, the fuel cell emits heat and water as by-products.
- 2.Fuel cells can be used for powering buildings and not for small devices like laptop computers.
- 3.Fuel cells produce electricity in the form of Alternating Current (AC).
Which of the statements given above is/are correct?
AnswerUPSC’s answer is (a).
A hydrogen fuel cell combines hydrogen with oxygen in an electrochemical reaction to produce electricity, with water and heat as by-products, so statement 1 is correct. Fuel cells come in many sizes and can power buildings, vehicles and small devices such as laptops, so statement 2 is wrong. They generate direct current, not alternating current, so statement 3 is wrong.
- 1. Pure hydrogen and oxygen give electricity, water and heat.
- 2. Fuel cells also power small devices such as laptops.
- 3. Fuel cells produce direct current.
How you could have got this
- If you were sure statement 3 is not correct, (b), (c) and (d) go: each of them includes 3.
What you needed to know: Fuel cells produce direct current.
Only (a) is left. You didn’t need statements 1 or 2.
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) Correct: only the water and heat by-products statement is right.
- (b) Wrong: statements 2 and 3 are false.
- (c) Wrong: fuel cells produce direct current, not alternating.
- (d) Wrong: statements 2 and 3 are false.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2015, General Studies Paper I, Series A. The paper on upsc.gov.in.