DC Theory LMS Practice Test

When resistors are in series, the same current flows through every resistor. Each resistor drops part of the total voltage equal to I times its resistance (V_i = I R_i). Since the current is the same through the chain, the total voltage across the series is the sum of these drops: V_total = I(R1 + R2 + ... + Rn). The total resistance is defined by V_total = I R_total, so R_total = R1 + R2 + ... + Rn. That is why you add the individual resistances to get the overall resistance in a series circuit. Dividing, subtracting, or multiplying would not describe how the voltage drops stack in a single current path.