In a circuit with resistors in series, what happens to current when one resistor's value increases?

• A. The current remains unchanged.
• B. The total current decreases; the same current flows through all components, but the higher total resistance reduces current.
• C. The current stops.
• D. The current increases.

Answer: (B)

In a series circuit, the current is the same through every component and is set by the source voltage and the total resistance: I = V / R_total. If one resistor’s value increases, the total resistance goes up, so the current must decrease. The same (now smaller) current flows through all components. The voltage across each resistor adjusts accordingly (V = I × R), so the resistor that increased tends to take a larger share of the source voltage while the overall current is reduced.