UPSC Prelims 2011 · GS Paper I
Question 7: Science and Technology
Microbial fuel cells are considered a source of sustainable energy. Why ?
- 1.They use living organisms as catalysts to generate electricity from certain substrates.
- 2.They use a variety of inorganic materials as substrates.
- 3.They can be installed in waste water treatment plants to cleanse water and produce electricity.
Which of the statements given above is/are correct ?
AnswerThe answer is (c).
A microbial fuel cell uses bacteria living on an electrode as catalysts to break down organic matter, releasing electrons that flow as an electric current. Because the fuel is organic waste, such as waste water, the cell can clean the water while producing electricity, which makes it a sustainable source of energy. The substrates are organic, not inorganic materials, so statement 2 is wrong. Remember: living catalysts plus organic substrates, and a use in waste water treatment.
- 1. Bacteria act as living catalysts that generate current from substrates.
- 2. The substrates are organic matter such as waste water, not inorganic materials.
- 3. Placed in waste water plants, they clean water and generate electricity.
How you could have got this
- If you were sure statement 2 is not correct, (b) and (d) go: each of them includes 2.
What you needed to know: The substrates are organic matter such as waste water, not inorganic materials.
- Then, if you were sure statement 3 is correct, (a) goes: it leaves 3 out.
What you needed to know: Placed in waste water plants, they clean water and generate electricity.
Only (c) is left. You didn’t need statement 1.
This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.
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) Misses statement 3 on waste water treatment.
- (b) Includes statement 2, which is wrong because the substrates are organic.
- (c) Right: living organisms as catalysts, and waste water treatment with power generation.
- (d) Includes the false statement 2.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2011, General Studies Paper I, Series A. The paper on upsc.gov.in.