Reed switches are being used in an electrical measuring circuit to monitor the position of a control rod in a reactor.
The reed switches are mounted in a column below the reactor vessel such that the control rod drive shaft passes by the reed switches as the control rod is withdrawn.
Which one of the following describes the action that causes the electrical output of the measuring circuit to change as the control rod is withdrawn?
A. An AC coil on the control rod drive shaft induces a voltage into each reed switch as the drive shaft passes by.
B. A metal tab on the control rod drive shaft mechanically closes each reed switch as the drive shaft passes by.
C. The primary and secondary coils of each reed switch attain maximum magnetic coupling as the drive shaft passes by.
D. A permanent magnet on the control rod drive shaft attracts the movable contact arm of each reed switch as the drive shaft passes by.
Show Answer
Answer: D
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