A device is labeled 15 A at 125 V. What is the maximum current it should safely carry before tripping or overheating?

• A. 10 A
• B. 15 A
• C. 20 A
• D. 25 A

Answer: (B)

A device rated 15 A at 125 V is designed to carry up to 15 amperes safely. The current rating is the limit that keeps the device from overheating in normal use; the voltage just shows the operating potential. At this rating, the maximum power the device would handle is P = V × I = 125 V × 15 A = 1,875 watts. If you push more than 15 A through it, heat buildup can occur and protective devices (like fuses or breakers) are expected to trip to prevent damage. So, the safe maximum current is 15 A.