In a series circuit with resistors R1, R2, R3, the total resistance is

• A. Max of R1, R2, R3.
• B. R1 + R2 + R3.
• C. R1 * R2 * R3.
• D. 1/(1/R1 + 1/R2 + 1/R3).

Answer: (B)

In a series circuit, the same current flows through every resistor, and the total voltage is the sum of the individual voltage drops. Each drop is I times its resistance, so V_total = I(R1 + R2 + R3). The total resistance is V_total divided by I, which gives R_total = R1 + R2 + R3. So the resistors in series simply add their resistances.

This fits the idea that adding more barriers to the same current increases the overall opposition by the exact amount each resistor contributes. The other expressions don’t describe series behavior: taking the maximum would ignore the combined effect of all resistors, a product isn’t how series resistance combines, and the reciprocal sum is the rule for parallel circuits.