RAS question
Fuel cells generate electricity through:
Correct answer: (B) Electrochemical reaction of hydrogen and oxygen.
Fuel cells generate electricity through the electrochemical reaction of hydrogen and oxygen, producing water and heat without combustion.
Explanation
A fuel cell is not a heat engine and it does not burn its fuel. In the standard hydrogen fuel cell described by the U.S. Department of Energy, hydrogen is supplied at the anode and oxygen is supplied at the cathode. A catalyst separates hydrogen molecules into protons and electrons. The electrons are forced through an external circuit, creating electric current, while the protons pass through the electrolyte. At the cathode, the protons, electrons and oxygen combine to form water, with heat also released. That is why the correct process is an electrochemical reaction between hydrogen and oxygen: chemical energy is converted directly into electricity, rather than first being converted into heat by combustion.
Why the other options are wrong
- (A) Nuclear fission splits atomic nuclei, while the given fuel-cell mechanism depends on hydrogen and oxygen reacting electrochemically.
- (C) Solar radiation is the energy input for solar cells, whereas fuel cells use chemical energy supplied by fuel and oxygen.
- (D) Combustion of fossil fuels releases energy by burning, but fuel cells generate current through an electrochemical process without combustion.
Concept
This tests the Science and Technology concept of electrochemical energy conversion. It recurs in RAS because fuel cells sit at the intersection of clean energy, hydrogen technology and basic applied chemistry.