Spin up exam 2- Q 49 and 50

[PE blues]

Can someone explain the answers?

 

[cali78]

That is just basic relay logic which you need to be familiar with. For question 49, when button "V" is pushed, relay "z" will get latched and contact "z" will energize relay "Y". When relay "Y" is energized the normally closed contact "Y" will become open and not provide a path to energize the green light. For question 50, when button "T" is pushed the latched "Z" contact will be in the de-energized state, so the normally open contact "Z" will ensure the green light is off.

You should understand what a latched relay is. It is common in relay logic and PLC's.

 

[PE blues]

I understand now. I guess I was looking for something like "green light remains off" in the answers instead of "green light turns off". "Green light turns off" gave me the presumption that the light was previously on, which is not possible because contact Z is open.

PS- Latching relay is also called auxiliary relay in case any one is wondering