In a series combination of resistors, they are connected end to end, meaning the total current flowing through the circuit is the same at every point, while the total voltage across the resistors is the sum of the individual voltages. The formula for calculating total resistance (R_total) in a series circuit is given by R_total = R_1 + R_2 + R_3 + ... This relationship indicates that the total resistance increases with each additional resistor added in series. The significance of understanding series circuits lies in their ability to affect the behavior of the current and voltage within electric circuits, which is foundational to the study of electricity.