Spot welding is used when two plates are placed:

Explanation:

Spot Welding

Spot welding is a type of resistance welding used primarily for joining two or more metal sheets. The process involves applying pressure and heat generated from an electric current to the weld area. It is commonly used in the automotive industry and for manufacturing metal furniture, appliances, and other products. The heat required for welding is generated by the resistance to the electric current passing through the metal sheets at the welding point. The key aspects of spot welding are:

• Pressure Application: The metal sheets are clamped together with electrodes that apply pressure to the weld area.

• Electric Current: A high current is passed through the electrodes, generating heat due to the resistance of the metal sheets.

• Weld Formation: The heat generated melts the metal at the interface, forming a weld nugget upon cooling.

• Cooling: The electrodes continue to apply pressure while the weld cools and solidifies.

Analyzing the Given Options

1. "One butting against the other."

   • This configuration refers to edge-to-edge joining, which is not suitable for spot welding.

2. "One next to the other." 

   • This configuration refers to side-by-side alignment, which is not appropriate for spot welding.

3. "One below the other." 

   • Correct Configuration: Spot welding is typically used for joining two sheets placed one below the other.

   • The electrodes are positioned on opposite sides of the sheets to apply pressure and conduct electric current.

4. "At right angles to each other." 

   • This configuration refers to joining at 90-degree angles, which is not typical for spot welding.