In a series circuit, the sum of the voltage drops across all components equals the

• A. The product of voltages
• B. Zero
• C. Each equals the source voltage
• D. The sum equals the source voltage

Answer: (D)

In a series circuit, the same current flows through every component, and the source provides a fixed amount of potential difference to the loop. The energy (voltage) lost across each component adds up to the total provided by the source. So, when you add all the voltage drops across the components, you recover exactly the source voltage. For example, if the source is 12 volts and the drops are 7 V and 5 V, their sum is 12 V. The other ideas don’t fit this distribution: you don’t multiply voltages to get the source, and the total isn’t zero unless you’re accounting for sign around the loop; an individual drop will equal the source voltage only if there’s a single component.