According to Ohm's law for a lamp with fixed supply voltage, what happens to wattage as resistance increases?

According to Ohm's law for a lamp with fixed supply voltage, what happens to wattage as resistance increases?

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

Answer: (A)

Power at a fixed supply voltage follows P = V^2 / R, so the wattage is inversely related to resistance. As resistance increases, the denominator grows and the power decreases. For example, if the voltage is 120 V and the resistance doubles, the power becomes half. The current also drops with increasing resistance (I = V / R), reinforcing the reduction in power. In a lamp, the filament’s resistance rises as it heats, so the wattage falls to its steady value rather than staying the same or increasing.

Power at a fixed supply voltage follows P = V^2 / R, so the wattage is inversely related to resistance. As resistance increases, the denominator grows and the power decreases. For example, if the voltage is 120 V and the resistance doubles, the power becomes half. The current also drops with increasing resistance (I = V / R), reinforcing the reduction in power. In a lamp, the filament’s resistance rises as it heats, so the wattage falls to its steady value rather than staying the same or increasing.