When two batteries are connected in series with a load resistor, the overall emf is the sum of the individual batteries' emfs. The total internal resistance is the sum of the individual internal resistances. The same current flows through each battery. The terminal voltage is the sum of the individual terminal voltages. Kirchhoff's loop rule gives the current. Although the series connection increases the supplied voltage, it also increases the equivalent internal resistance. The equivalent terminal voltage can be generalized for N batteries in series. When two batteries with identical emfs are connected in parallel to a load resistor, the total emf is the same as the individual batteries' emfs. Applying Kirchhoff's junction rule at the common node, Kirchhoff's loop rule for loop 1, and for loop 2, the equations are solved to determine the load current via the equivalent resistance. Thus, the terminal voltage is obtained. The parallel connection reduces the internal resistance and can produce a large current. The equivalent terminal voltage expression can be generalized for N batteries in parallel.