In the series circuit above, what is the voltage drop across R2?

• A. 3.6 V
• B. 7.2 V
• C. 6.0 V
• D. 1.2 V

Answer: (A)

In a series circuit, the same current flows through every component, and the voltages across all components add up to the source voltage. The voltage drop across a particular resistor is determined by how large its resistance is relative to the total resistance: V_R2 = V_source × (R2 / R_total). This comes from Textbook relationships: the current is I = V_source / R_total, and V_R2 = I × R2, which simplifies to the same ratio form. So the voltage drop across the second resistor is the portion of the total voltage proportional to its share of the total resistance. The option that matches that calculated share, given the circuit’s values, is the correct one because it satisfies both the equal current in a series path and the sum of drops equaling the source voltage.