When two lamps are added in series, what happens to the total resistance?

When two lamps are added in series, what happens to the total resistance?

• A. Decreases
• B. Increases
• C. Stays the same
• D. Fluctuates

Answer: (B)

When components are in series, the same current flows through each one, and the resistances simply add together. The total resistance seen by the power source is the sum of the individual resistances: R_total = R1 + R2. Adding another lamp adds another resistance in the path, so the overall opposition to current increases. With a fixed supply voltage, the current is I = V / R_total, so as R_total goes up, the current decreases. In short, placing two lamps in series raises the total resistance.

When components are in series, the same current flows through each one, and the resistances simply add together. The total resistance seen by the power source is the sum of the individual resistances: R_total = R1 + R2. Adding another lamp adds another resistance in the path, so the overall opposition to current increases. With a fixed supply voltage, the current is I = V / R_total, so as R_total goes up, the current decreases. In short, placing two lamps in series raises the total resistance.