How do we produce hydro electricity

The y form of iron is known as: a) ferrite b) cementite c) perlite d) austenite

The temperature of air decreases as it is compressed by an adiabatic compressor. a)- true b)- false

Which of the following ziegler nichols tuning methods the response of the controller to a step input should exhibit an s-shaped curve? a)-open loop mode b)-closed loop mode c)-both modes (open & closed) d)-none of the modes (open & closed)