The electrodes of a spot welder are made of ___________ so there is little electrical resistance. 22. Name...

21. The electrodes of a spot welder are made of ___________ so there is little electrical resistance.
22. Name one of two technologies that a robot uses to help it weld precisely.
23. The process used to weld plastic is known as _______________ welding.
24. This process uses ultrasonic _______________ waves to produce heat and weld the plastic.
25. The process used to weld the coffee mug used _____________ friction to produce the necessary heat.