What is a series connection of cells and what is a parallel connection of cells? Explain.

(N/A) $1$. Series Connection of Cells: When cells are connected in series,the positive terminal of one cell is connected to the negative terminal of the next cell. In this arrangement,the total electromotive force $(EMF)$ is the sum of the individual EMFs of the cells $(E_{eq} = E_1 + E_2 + ... + E_n)$,and the total internal resistance is the sum of the individual internal resistances $(r_{eq} = r_1 + r_2 + ... + r_n)$. This configuration is used to increase the total voltage output.
$2$. Parallel Connection of Cells: When cells are connected in parallel,all positive terminals are connected together and all negative terminals are connected together. In this arrangement,the equivalent $EMF$ remains equal to the $EMF$ of a single cell (if all cells are identical,$E_{eq} = E$),while the total internal resistance decreases $(1/r_{eq} = 1/r_1 + 1/r_2 + ... + 1/r_n)$. This configuration is used to increase the current capacity and reduce the total internal resistance.