Automation System
The Ziegler-Nichols method:

is a method of control
None of these
a and b above
can be used to determine gain factors of a PI loop
is a graphical solution method

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Automation System
Stepping motors:

do not require commutators
All of these
can be built to index different amounts by changing the pole configuration
can run both clockwise and counterclockwise
can run at varying speeds

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