Cells in Series and in Parallel

Introduction

Cells are commonly known as electrochemical cells, which are the main suppliers of electric energy. The energy or current is gathered from the chemical reactions that normally occur between the cells. Also, the cells are sometimes denoted as batteries, which everyone uses in their daily life to perform several activities related to electrical supplies. However, it is important to understand for acknowledging the cells in series and in parallel that a collection of cells creates the battery that functions differently when placed in different circuits. Thus the batteries are the devices that contain a considerable amount of electrochemical cells attached with an external connection in the form of series or parallel so that they can supply the required amount of power to several devices. 

Definition of cells

Cells in series and in parallel are the chemical reactions that produce electricity that is shared with the help of the two terminals present in each cell. The two terminals of cells are further classified as:

• Cathode: It is the terminal of the cell that helps the current flow to perform in the outside direction, which means outside the circuit or device. 

• Anode: It is the inner terminal that helps the current to enter and leave the circuit. These are thus also known as the incoming source, including the current’s exit to and from the device. 

Further, these are built with electrodes and electrolytes. These are commonly known as the anode and cathode. 

EMF

The EMF is important in cells in series and in parallel as it helps identify the potential difference between the positive and negative electrodes. The EMF is also known as the electromotive force, which initially results in the flow of current in the cell. This further functions when the current is not present in the cell or the cell is placed over an open circuit. 

The S.I unit of EMF in Cells is Volte (V), which is denoted with the formula, 

V= IR+Ir

Here, V= Volte, or EMF, 

I= Current, 

R= Load resistance in Ohms, 

r= internal resistance of cells in Ohms. 

Internal Resistance

This is the resistance obtained from the electrolyte, including the electrodes, that normally occurs when the current flows in the circuit. The flow of the energy is further opposed or buried by the electrodes or electrolytes, which creates the internal resistance and are commonly denoted with the letter ‘r’. 

For instance, let’s assume a cell with two electrolytes that are further connected with each other with the help of external resistance. This is further denoted by ‘R’. The current that will flow is further denoted by the cells in a parallel formula:

For closed circuit: V= V1+V2-Ir 

Here V1 and V2 are the initial difference, 

And Ir is the drop across the internal resistance. 

Thus from this, it can be included that V= e- Ir

Where e denotes the EMF or Volte, and V is the difference between the two electrodes. 

Or, IR = e-Ir

However, this is obtained only at the time of closed-circuit, where the resistance will play its part. However, these are not constant and vary from one cell to another. 

How do the Cells Connect to a Device? 

The cells normally connect with the help of cells in series and in parallel connections, which are further elaborated:

• Cells in Series

The components are attached in a sequential form of components for series connection. This means that the cells are connected from one end to the other end so that the same amount of current is passed from each cell of the circuit. 

Thus, when the cells perform the series connection, then the total electromotive force is joined with the EMF of the battery from the individual cell. 

For instance, when you notice that the positive end of the first battery is attached with the negative end of the first cell, then the second battery is connected to the positive end of the positive cell and forms the series combination of the cell. 

Advantages

The cells present in the series connection can be beneficial as it allows enjoying a higher system current resulting in a lower system of voltage. The lower voltage further shows that a thin wire can make it suffer from the drop of the voltage in a system. 

Resistance of Cells in Series

If E is obtained from the entire EMF of the cells combined with “n” number of cells, the sequence will form, including E1, E2, E3, En. Here, the equation will help calculate the cells’ EMF, especially for this type of connection. Equivalent emf of combined system will be,

Eeq = E1 +  E2 + E3 + ………..+ En

 Similarly, the r1, r2, r3 and rn are the internal resistances of the cells that provide the total amount of internal resistance present in the individual battery. The equivalent resistance of whole combination we will be

req = r1 + r2 + r3 + ……….+rn

• Cells in Parallels

The parallel connection is different in the cells in series and in parallel. However, it is donated with the help of the connectivity of the parts present in the electrical circuit and the other parts. Thus the parallel-connected cells are the amount that gets equally divided among each cell. Further, the internal resistance of the parallel combination of cells formula is R = (1/R1 + 1/R2 + 1/R3 +… 1/Rn)-1. 

Here the negative ends of the cells get attached with the positive ends to form the connection in the circuit. Also, the parallel combination of cells formula can help find the value of the electromotive force and the internal resistance of the cells. For instance, if the EMF in each cell is the same, the battery added with the ‘n’ number of cells forms a parallel connection similar to the electromotive force. However, in the above equation, R denotes the internal resistance present in the entire combination. 

Resistance of Cells in Parallel Connection

You already know that cells in the parallel formulas are already obtained from the Ohms Laws. However, the resistance of this can be understood when the electromotive force of an individual cell is described as E, where the internal resistance of cells is denoted with the help of r. For instance, the cells present in the series combination, where the EMF of the individual battery is pointed as nE. Similarly, a similar resistance will be shown with nr’s help. In this case, when the cells create a parallel combination, the similar internal resistance is denoted as nr/m.

Conclusion

Thus the cells in series and in parallel contain a huge amount of difference that include the connection shared by the components. For instance, for series, the sharing connection is equal to the amount of current; however, for parallel, the components hold the same amount of difference among them. This means that the components remain connected with various paths and witness the same amount of voltage provided to each component in the circuit. However, for a series of cells, components have a single path to share the same amount of energy through the various components of the circuit.