Question

Batteries and fuel cells are very useful forms of galvanic cell. Any battery or cell that we use as a source of electrical energy is basically a galvanic cell. However, for a battery to be of practical use it should be reasonably light, compact and its voltage should not vary appreciably during its use. There are mainly two types of batteries — primary batteries and secondary batteries. In the primary batteries, the reaction occurs only once and after use over a period of time the battery becomes dead and cannot be reused again, whereas the secondary batteries are rechargeable. Production of electricity by thermal plants is not a very efficient method and is a major source of pollution. To solve this problem, galvanic cells are designed in such a way that energy of combustion of fuels is directly converted into electrical energy, and these are known as fuel cells. One such fuel cell was used in the Apollo space programme. Answer the following questions:

Assertion: Mercury cell does not give steady potential. Reason: in the cell reaction, ions are not involved in solution.

Which one of the following statements is correct regarding the dry cell? (P) Zinc container acts as an anode in dry cell. (Q) Zinc container touches the paste of MnO2 and carbon. (R) Dry cell can be charged easily. (S) Graphite rod acts as a cathode in dry cell.