Why is the combination of cells done? Write its methods.

(N/A) single cell often cannot provide the necessary voltage or current required for a specific circuit. In such conditions,by connecting more than one cell in different combinations,the desired voltage or current can be obtained. This process is known as the combination of cells.
There are three primary methods of combining cells:
$(1)$ Series connection: Used to increase the total electromotive force $(EMF)$ of the circuit.
$(2)$ Parallel connection: Used to increase the total current capacity and reduce the internal resistance of the circuit.
$(3)$ Mixed connection: Used to achieve an optimal balance between voltage and current requirements.