When a lead-acid battery is in fully charged condition, the color of its positive plate is

dark grey
brown
dark brown
none of above

The correct answer is: A. dark grey

When a lead-acid battery is in a fully charged condition, the color of its positive plate is dark grey. This is because the lead sulfate on the plate has been converted to lead dioxide. Lead dioxide is a dark grey powder.

The other options are incorrect because:

  • Option B: brown is the color of the positive plate when the battery is in a discharged condition.
  • Option C: dark brown is the color of the positive plate when the battery is in a very discharged condition.
  • Option D: none of the above is the correct answer.