Magnetic overload relays react only to current excess and are not affected by ______?

• A. Humidity
• B. Voltage fluctuations
• C. Temperature
• D. Mechanical vibration

Answer: (C)

Magnetic overload relays protect motors by reacting to current levels, not to heat or other environmental factors. The trip action is driven by electromagnetic flux created by the current flowing through the circuit, so the device responds to a current overload regardless of ambient temperature within normal ranges. This is different from thermal overload relays, which rely on heat to bend a bimetal element and are therefore affected by temperature. In other scenarios, humidity or mechanical vibration could influence contact reliability, and voltage fluctuations can change current, but the magnetic trip itself is governed by current magnitude, not temperature.