What kind of motor controller has a number of resistors arranged so that they can be included in the motor circuits as needed A. Magnetic
B. Faceplate
C. drum
D. semiautomatic

What is the heat treatment of metals? what is the benefit of it? why and how it's useful? answer in details, do not write by hand.

Ahelical coil spring has a mean diameter of 50 mm, a wire diameter of 5.5 mm and is wound with a pitch of 10 mm. the spring steel has an ultimate strength of 1250 mpa. find the force needed to compress the spring solid and the wire stress in this condition. state whether the spring will return to its initial length.

Tech a says never use a water hose to clean up dust after a repair. tech b says never use a floor scrubber to clean up dust after repairs. who is correct?