In a series circuit, the total resistance to current flow is equal to the sum of the resistances. This summation is with respect to what parameter?

• A. Voltage
• B. Current
• C. Resistance
• D. Current flow

Answer: (D)

In a series circuit, the current that flows is the same through every component, so the resistances add up to form a single total opposition that this same current encounters. The total resistance is what the current “sees” as it travels from the source, and Ohm’s law (V = I R) ties that total resistance to the supply voltage and the current. Therefore, the summation of the resistances is with respect to the current flow—the current is the parameter being affected by that total resistance.

Noting differences helps: voltages across components in series add to equal the supply voltage, not the resistances themselves. And since the current is the same through all elements in series, you don’t sum currents.