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?

Let's evaluate the statements about fuel cells:

1. If pure hydrogen is used as a fuel, the fuel cell emits heat and water as by-products: This statement is correct. A primary advantage of hydrogen fuel cells is their clean operation. When pure hydrogen reacts with oxygen, the only by-products are water (H2O) and heat, making them a highly environmentally friendly energy source.
2. Fuel cells can be used for powering buildings and not for small devices like laptop computers: This statement is incorrect. Fuel cells come in various sizes and power outputs. While large fuel cells can indeed power buildings and vehicles, miniature fuel cells are also developed and used for small portable electronic devices like laptops, cell phones, and cameras.
3. Fuel cells produce electricity in the form of Alternating Current (AC): This statement is incorrect. Fuel cells generate electricity through an electrochemical process, similar to batteries. They produce Direct Current (DC) electricity. While DC can be converted to AC using an inverter for specific applications, the direct output of a fuel cell is DC. Therefore, only statement 1 is correct.