Examoogle • User • info@examoogle.com • EE-2024-8821

Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked

ElectricalBasic Electrical

Prev Next

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

dark grey

brown

dark brown

none of the above

Correct Answer

Concept & PrincipleElectricalBasic Electrical

Option B

brown

Quick Summary: In a fully charged lead-acid battery, the active material of the positive plate consists of Lead Peroxide ($PbO_2$), which exhibits a characteristic dark brown color. The negative plate, composed of sponge lead ($Pb$), appears grey or slate grey.

💡 Explanation

In a fully charged lead-acid battery, the active material of the positive plate consists of Lead Peroxide ( $PbO_2$ ), which exhibits a characteristic dark brown color. The negative plate, composed of sponge lead ( $Pb$ ), appears grey or slate grey.

🔢 Key Formulas

$PbSO_4 + 2H_2O \xrightarrow{\text{charge}} PbO_2 + H_2SO_4 + H_2$ — Positive plate charging reaction

⚙️ Working Principle

During the charging process, the electrical energy induces a chemical reaction where lead sulfate ( $PbSO_4$ ) on the plates is converted. At the positive plate, $PbSO_4$ reacts with the electrolyte and water to form Lead Peroxide ( $PbO_2$ ), which is dense and dark brown in color. The reaction is: $PbSO_4 + 2H_2O + SO_4°{2-} \rightarrow PbO_2 + 2H_2SO_4$ .

📌 Key Points

▸
Positive plate is made of Lead Peroxide ( $PbO_2$ ).
▸
Negative plate is made of Sponge Lead ( $Pb$ ).
▸
State of charge can be visually estimated by plate color.
▸
Fully discharged plates appear white due to the accumulation of lead sulfate.

✅ Advantages

▸
High surge current capability
▸
Low self-discharge rate compared to other rechargeable chemistries

❌ Disadvantages / Limitations

▸
Low energy-to-weight ratio
▸
Risk of sulfation if left in a discharged state

🛠️ Applications / Uses

▸
Automotive starting, lighting, and ignition systems
▸
Uninterruptible Power Supplies (UPS)

📄 Additional Information

▸
As the battery discharges, the dark brown $PbO_2$ is converted back to white $PbSO_4$ , causing the plate color to lighten.
▸
Option A (Dark Grey) is incorrect as it typically describes the negative plate or a partially discharged positive plate.

📊 Diagram / Illustration

✅

C is correct — The positive plate of a fully charged lead-acid battery is dark brown because it consists of lead peroxide ( $PbO_2$ ).

Core Concepts Used

Click any tag to open in AI Tutor

Electrochemical energy storage Active plate materials Lead-acid charging chemistry

💡 EXAM TIP

Always remember: $PbO_2$ (positive) is dark brown, $Pb$ (negative) is grey, and $PbSO_4$ (discharged/sulfated) is white/light grey.

Discussion (0)

Loading discussion...

Prev Next

Correct Answer

Related Questions

Discussion (0)