A 2 W resistor dissipates 1.5 W. What percentage of its rating is being used?

A 2 W resistor dissipates 1.5 W. What percentage of its rating is being used?

• A. 25%
• B. 75%
• C. 50%
• D. 125%

Answer: (B)

This tests how resistor power rating relates to actual dissipation. A resistor rated at 2 W can safely dissipate up to 2 W. If it’s dissipating 1.5 W, that’s 1.5 divided by 2, which equals 0.75, i.e., 75% of its rating. So the resistor is operating at 75% of its capacity. It’s not 125% (that would require 2.5 W, beyond the rating), and it’s not 50% or 25% (that would be 1 W or 0.5 W, respectively).

This tests how resistor power rating relates to actual dissipation. A resistor rated at 2 W can safely dissipate up to 2 W. If it’s dissipating 1.5 W, that’s 1.5 divided by 2, which equals 0.75, i.e., 75% of its rating. So the resistor is operating at 75% of its capacity. It’s not 125% (that would require 2.5 W, beyond the rating), and it’s not 50% or 25% (that would be 1 W or 0.5 W, respectively).