Resistance is additive in a series circuit.

• A. Multiplicative
• B. Zero
• C. Additive
• D. Inversely proportional

Answer: (C)

In a series circuit, the total resistance is the sum of the individual resistances. This happens because the same current flows through every component, and each resistor drops a portion of the total voltage proportional to its resistance. Using V = IR, the voltage across each resistor is V_i = I R_i. The total supply voltage is the sum of these drops: V_total = V1 + V2 + ... = I(R1 + R2 + ...). But V_total also equals I times the total resistance, V_total = I R_total. Since the current is not zero, you can cancel I and get R_total = R1 + R2 + ... So the total resistance adds up.

Example: two resistors of 2 Ω and 3 Ω in series give a total of 5 Ω. With a 10 V source, the current is 2 A, and the voltage drops are 4 V and 6 V, which add to the total supply voltage.

The additive description matches this behavior. Multiplicative, zero, or inversely proportional would not describe how resistance behaves in a series path.