Red Seal Welder Practice Exam

What principle does resistance spot welding operate on?

1. Heat generated by chemical reactions

2. Mechanical pressure applied during welding

3. Heat generated by electrical resistance

4. Ultrasonic vibrations to join materials

The correct answer is: Heat generated by electrical resistance

Resistance spot welding operates on the principle of heat generated by electrical resistance. In this process, two metal surfaces are brought together, and an electrical current is passed through them. The resistance to the flow of electricity at the interface of the metal pieces generates heat due to the Joule heating effect. This localized heating melts the metal, allowing them to fuse together upon cooling. This method is advantageous in welding thin metal sheets and provides a strong joint quickly and efficiently. It is widely used in various industries, especially in automotive manufacturing, due to its speed and effectiveness in producing high-quality welds. The other options describe different processes: chemical reactions do not play a role in resistance spot welding, mechanical pressure is generally associated with processes like forge welding or mechanical joining methods, and ultrasonic vibrations are utilized in ultrasonic welding, which is a distinct technique that employs high-frequency sound waves to join materials.