Understanding Batteries Connected in Series

When batteries are connected in series, the positive terminal of one battery is connected to the negative terminal of the next battery, and so on. This arrangement is commonly used to increase the total voltage supplied by the battery pack.

Let's explore what happens to the voltage and capacity when batteries are connected in series.

Impact on Voltage in Series Connection

When batteries are connected in series, their voltages add up. If you have multiple batteries, each with a voltage of \(V\), and you connect \(n\) such batteries in series, the total voltage of the series combination is the sum of the individual voltages.

For example, if you connect two 1.5 Volt (V) batteries in series, the total voltage will be \(1.5 \, \text{V} + 1.5 \, \text{V} = 3.0 \, \text{V}\). If you connect three 1.5V batteries in series, the total voltage will be \(1.5 \, \text{V} + 1.5 \, \text{V} + 1.5 \, \text{V} = 4.5 \, \text{V}\).

Mathematically, for \(n\) identical batteries each with voltage \(V\):

\(V_{\text{total}} = n \times V\)

Impact on Capacity Rating in Series Connection

The capacity rating of a battery, often measured in Ampere-hours (Ah) or milliampere-hours (mAh), indicates how long the battery can supply a certain amount of current. When batteries are connected in series, the total capacity rating remains the same as the capacity of a single battery, assuming all batteries have the same capacity.

The current flows through each battery in the series chain sequentially. Therefore, the chain can only supply current for as long as the lowest-capacity battery can sustain that current. If all batteries have the same capacity, the total capacity of the series combination is limited by the capacity of any single battery in the series.

For example, if you connect two 1000 mAh batteries in series, the total capacity is still 1000 mAh. You get 3V (from 1.5V + 1.5V), but you can still only draw 1000 mAh before the battery pack is depleted.

Mathematically, for \(n\) identical batteries each with capacity \(C\):

\(C_{\text{total}} = C\)

Analyzing the Given Options

Let's examine each option based on our understanding of batteries in series:

1. The capacitance doubles, the voltage rating remains the same.
   • Incorrect. Voltage increases (doubles if two batteries are connected), and capacity (often referred to as capacity rating) remains the same, not doubles. The term "capacitance" is sometimes used loosely for battery capacity, but even then it doesn't double in series.
2. The voltage doubles, the capacitance rating doubles.
   • Incorrect. While voltage doubles (when two identical batteries are in series), the capacity rating remains the same, it does not double.
3. Voltage remains the same, capacitance stays the same.
   • Incorrect. Voltage increases (doubles for two identical batteries in series), it does not remain the same.
4. The voltage doubles, the capacity rating remains the same.
   • Correct. When two identical batteries are connected in series, the total voltage is the sum of individual voltages (doubling if they are identical), and the total capacity rating is equal to the capacity of a single battery (remaining the same).

Conclusion

Connecting batteries in series increases the total voltage while keeping the overall capacity rating the same (assuming identical batteries are used). This setup is useful when a higher operating voltage is required, but the same current duration as a single battery is sufficient.

Revision Table: Battery Connections

Additional Information: Battery Basics and Connections

Batteries are electrochemical devices that convert stored chemical energy into electrical energy. They have a positive terminal and a negative terminal, creating a potential difference (voltage) between them.

• Voltage: Represents the electrical potential energy per unit charge. It's the "pressure" that pushes electrons through a circuit.
• Capacity: Represents the total amount of electrical charge a battery can deliver over time. It's usually measured in Ampere-hours (Ah) or milliampere-hours (mAh), where 1 Ah means the battery can supply 1 Ampere of current for 1 hour.

Understanding how to connect batteries (series or parallel) is crucial for designing power systems for various applications, from simple flashlights to electric vehicles.

• Series Connection: Used to increase the total voltage. The current drawn by the load passes through each battery in the series string.
• Parallel Connection: Used to increase the total capacity (and thus runtime) while maintaining the voltage of a single battery. The total current drawn by the load is shared among the parallel-connected batteries.