Which statement about voltage drop in a series circuit is true?

• A. The voltage drop across each load is always equal.
• B. The sum of the voltage drops across all loads equals the source voltage.
• C. The voltage across the last load is zero.
• D. The source voltage is unaffected by the loads.

Answer: (B)

In a series circuit, the same current flows through every component, and each load drops a portion of the source voltage proportional to its resistance. The total voltage provided by the source must balance the whole circuit, so the sum of all those voltage drops around the loop equals the source voltage. That’s why the statement that the sum of the voltage drops across all loads equals the source voltage is true. If the resistances are not all equal, the individual drops will differ, but they still add up to the source voltage. The voltage across the last load isn’t necessarily zero, and while an ideal voltage source would keep its voltage fixed, the way that voltage is divided among loads depends on their resistances.