When a lead-acid battery is completely charged, the hue of its positive plate is__________?
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Answer: C. dark brown
Explanation
When a lead-acid battery is completely charged, its positive plate consists of lead peroxide. This specific chemical compound gives the positive plate a characteristic dark brown hue. Visual inspection of plate color is a traditional method used by technicians to assess charge state. Lead peroxide forms on positive plates during the charging process as lead sulfate reacts with water. The negative plate, by contrast, appears as spongy grey metallic lead when fully charged. Plate color changes gradually from light grey to dark brown as the electrochemical conversion completes.
Battery rebuilders inspect internal plate colors during overhauls to diagnose historical charging problems. Understanding plate appearance helps technicians verify whether a battery has achieved complete chemical recovery. Proper charging ensures that all active material successfully converts to its dark brown lead peroxide form. Dark grey or standard grey typically represents discharged plates or negative plate material composition. Plain brown without the dark shade indicates an intermediate or incomplete state of charge. None of above is incorrect because dark brown accurately describes the fully charged positive plate color.
- Subject
- Engineering
- Category
- Electrical Engineering
- Topic
- —
- Difficulty
- medium
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