## Cells in Series and in Parallel – Class 12 | Chapter – 3 | Physics Short Notes Series PDF for NEET & JEE

Cells in Series and in Parallel: When multiple cells are connected together in a circuit, they can be connected either in series or in parallel. In a series connection, the cells are connected one after the other, such that the positive terminal of one cell is connected to the negative terminal of the next cell. This means that the same current flows through all of the cells, but the total voltage of the circuit is equal to the sum of the voltages of the individual cells. For example, if three cells with a voltage of 1.5V each are connected in series, the total voltage of the circuit would be 4.5V.

In a parallel connection, the positive terminal of each cell is connected to the positive terminal of all the other cells, and the negative terminal of each cell is connected to the negative terminal of all the other cells. This means that the same voltage is across all of the cells, but the total current of the circuit is equal to the sum of the currents of the individual cells. For example, if three cells with a current of 1A each are connected in parallel, the total current of the circuit would be 3A.

## Advantages of Cells in Series and in Parallel

### Advantages of Cells in Series

There are several advantages to connecting cells in series:

• Increased voltage: When cells are connected in series, the total voltage of the circuit is equal to the sum of the voltages of the individual cells. This allows for a higher voltage output, which may be necessary for certain applications.
• Increased energy capacity: Connecting cells in series increases the energy capacity of the circuit, as the energy stored in each cell is added together.
• Improved stability: Connecting cells in series can improve the stability of the circuit, as any variations in the voltage of individual cells will tend to cancel each other out.
• Improved reliability: In a series connection, if one cell fails, the entire circuit will not be affected, as the other cells will continue to operate normally.
• Simplified design: Connecting cells in series is a simple way to increase the voltage of a circuit, as it only requires connecting the positive terminal of one cell to the negative terminal of the next cell.

### Advantages of Cells in Parallel

There are several advantages to connecting cells in parallel:

• Increased current: When cells are connected in parallel, the total current of the circuit is equal to the sum of the currents of the individual cells. This allows for a higher current output, which may be necessary for certain applications.
• Improved capacity utilization: Connecting cells in parallel can improve the utilization of the total capacity of the cells, as the current can be distributed among all cells, allowing each cell to operate at a lower current and potentially extending the life of the cells.
• Improved reliability: In a parallel connection, if one cell fails, the overall voltage of the circuit will not be affected, as the other cells will continue to provide voltage.
• Increased safety: In a parallel connection, if one cell fails, the overall voltage of the circuit will not be affected, reducing the risk of electrical shock or damage to other components in the circuit.
• Simplified design: Connecting cells in parallel is a simple way to increase the current of a circuit, as it only requires connecting the positive terminal of each cell to the positive terminal of all the other cells, and the negative terminal of each cell to the negative terminal of all the other cells.

## Disadvantages of Cells in Series and in Parallel

### Disadvantages of Cells in Series

There are several disadvantages to connecting cells in series:

• Single point of failure: If one cell in a series connection fails, the entire circuit will stop functioning, as the voltage of the failed cell will drop to zero, reducing the overall voltage of the circuit.
• Unequal voltage distribution: If the cells in a series connection have slightly different characteristics, such as different internal resistances or different voltages, the voltage may not be distributed equally among all cells, leading to some cells carrying more voltage than others. This can cause one or more cells to fail prematurely, reducing the overall reliability of the circuit.
• Increased internal resistance: The internal resistance of a series connection is equal to the sum of the internal resistances of the individual cells, which can increase the power loss due to heat generated by the internal resistance.
• Increased cost: Connecting cells in series often requires additional components, such as additional wiring, connectors, and protection circuits, which can increase the overall cost of the circuit.
• Complex design: Connecting cells in series can be more complex than connecting cells in parallel, as it requires careful consideration of the characteristics of each individual cell to ensure that the voltage is distributed evenly and that the overall circuit operates correctly.

### Disadvantages of Cells in Parallel

There are several disadvantages to connecting cells in parallel:

• Unequal current distribution: If the cells in a parallel connection have slightly different characteristics, such as different internal resistances or different capacities, the current may not be distributed equally among all cells, leading to some cells carrying more current than others. This can cause one or more cells to fail prematurely, reducing the overall reliability of the circuit.
• Increased risk of short circuits: Connecting cells in parallel increases the risk of a short circuit occurring, as there are more points of electrical connection, increasing the chance of a fault occurring.
• Increased internal resistance: The internal resistance of a parallel connection is lower than the internal resistance of an individual cell, which can increase the power loss due to heat generated by the internal resistance.
• Increased cost: Connecting cells in parallel often requires additional components, such as additional wiring, connectors, and protection circuits, which can increase the overall cost of the circuit.

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