In a series circuit, what is the total resistance relative to the individual resistances?

• A. The product of the resistances
• B. The reciprocal of the sum
• C. The sum of the resistances
• D. The difference between largest and smallest

Answer: (C)

In a series circuit, the same current flows through every component, and the voltages across the resistors add up to the total supply voltage. Since each resistor drops voltage proportional to its resistance (V = IR) and the current is the same through all of them, the total voltage is V_total = I(R1 + R2 + ...). Rearranging gives the total resistance as R_total = V_total / I = R1 + R2 + ... — you simply add the individual resistances. For example, 4 ohms plus 6 ohms in series equals 10 ohms. The other forms don’t apply here: a product or reciprocal of a sum relates to parallel arrangements, and a difference between values isn’t how series resistance is combined.