Question

Maintenance-free batteries, now in use in place of common batteries, have:
A) Electrodes made of a lead-lead oxide
B) Electrodes made of calcium-containing lead alloy
C) Non-aqueous solvents as medium
D) Platinum electrodes

Answer 1

Hint: Maintenance-free batteries do not require maintenance of electrolytes like traditional common batteries. Maintenance-free batteries are permanently sealed. Alloy use for making electrodes of maintenance-free batteries is different from the common batteries.

Complete answer:
Maintenance-free batteries, now in use in place of common batteries as they do not need refilling of electrolytes at regular intervals. Common batteries have removable caps while maintenance-free batteries have fixed caps.

In common batteries, electrodes are made of lead-lead oxide so it is known as lead-acid batteries. These are rechargeable batteries. Thus option (A) Electrodes made of lead-lead oxide is incorrect.

Grids of maintenance-free batteries are made up of calcium-containing lead alloy. The calcium content in alloy varied in the range of 0.06% to 0.1% however the tin content is about 0.1-0.8%. These are non-rechargeable batteries. Thus, the correct option is (B) Electrodes made of calcium-containing lead alloy.

Aqueous solvents are used as a medium in maintenance-free batteries. Thus, option (C) Non-aqueous solvents as a medium are incorrect.

Electrodes of maintenance-free batteries are made up of calcium-containing lead alloy and not platinum electrodes. Thus, option (D) Platinum electrodes are incorrect.

Thus the correct answer is option ‘B’.

Note: The main difference between common batteries and maintenance-free batteries is the alloy used for making electrodes. In common batteries, the negative plate is made up of lead and the positive plate is made up of lead oxide. Electrodes of maintenance-free batteries are made up of calcium-containing lead alloy.