Understanding Battery Nominal Voltage and Cell Types

The question asks us to identify the type of battery cell used when its nominal voltage is given as 1.2 V. The nominal voltage is the typical or average voltage of a battery cell during discharge. Different battery chemistries have characteristic nominal voltages.

Analyzing the Nominal Voltages of Common Battery Types

Let's look at the typical nominal voltages for the battery types provided in the options:

• Lithium ion: Lithium-ion battery cells typically have a nominal voltage of around \(3.6 \text{ V}\) or \(3.7 \text{ V}\). These are commonly used in portable electronics.
• Lead acid: Lead-acid battery cells have a nominal voltage of \(2.0 \text{ V}\) per cell. Car batteries are often made of multiple lead-acid cells connected in series.
• Nickel cadmium (NiCd): Nickel-cadmium battery cells have a nominal voltage of \(1.2 \text{ V}\) per cell. They were historically popular for many applications due to their durability and ability to handle high discharge rates, although their use has declined due to cadmium toxicity and memory effect.
• Zinc silver oxide: Zinc-silver oxide battery cells, also known as silver-oxide batteries, have a nominal voltage of around \(1.55 \text{ V}\). They are often used in small devices like watches and hearing aids.

Matching the Given Voltage to the Battery Type

The question states the nominal voltage of the battery cell is \(1.2 \text{ V}\). Comparing this value to the typical nominal voltages of the options:

• Lithium ion: \(3.6 \text{ V}\) - \(3.7 \text{ V}\)
• Lead acid: \(2.0 \text{ V}\)
• Nickel cadmium: \(1.2 \text{ V}\)
• Zinc silver oxide: \(1.55 \text{ V}\)

The nominal voltage of \(1.2 \text{ V}\) directly corresponds to the typical nominal voltage of a Nickel cadmium cell. Therefore, the type of cell used is Nickel cadmium.

Summary Table of Nominal Voltages

From the table, it is clear that a nominal voltage of \(1.2 \text{ V}\) is characteristic of Nickel cadmium cells (and also Nickel-Metal Hydride cells, which is not an option here). Based on the provided options, Nickel cadmium is the correct match for a \(1.2 \text{ V}\) nominal voltage cell.

Revision Table: Key Characteristics of Battery Types

Additional Information on Battery Cells and Voltage

The voltage of a battery cell is determined by the electrochemical reaction happening inside it. Different materials used as electrodes and electrolyte result in different potential differences, which is the cell voltage.

• Primary Cells: These are non-rechargeable batteries (e.g., standard alkaline AA/AAA batteries). They are designed for single use, as the chemical reactions are not easily reversible.
• Secondary Cells: These are rechargeable batteries (e.g., Li-ion, NiCd, NiMH, Lead-acid). The chemical reactions can be reversed by applying an external voltage, allowing the battery to store energy again.
• Nominal Voltage vs. Open Circuit Voltage: Nominal voltage is a reference value. The actual voltage of a battery cell varies depending on its state of charge, temperature, and the current being drawn from it. Open circuit voltage (OCV) is the voltage across the terminals when no load is connected. OCV decreases as the battery discharges.
• Battery Packs: To achieve higher voltages or capacities, individual cells are often combined into battery packs. Cells can be connected in series to increase voltage (e.g., three 1.2 V NiCd cells in series make a 3.6 V battery pack) or in parallel to increase capacity.

Understanding the nominal voltage is a quick way to initially identify the likely chemistry of a battery cell or pack, although looking at the labeling is the most reliable method.