Cut-off governing of steam engines: what parameter is varied to control output? Context: In cut-off governing, the point of admission is altered while speed/load change, without throttling the inlet pressure. Choose what is actually controlled under cut-off governing.

Concept
In cut-off governing, the governor varies the admission period (cut-off) so that the quantity/volume of steam admitted each cycle changes. The supply pressure is not deliberately throttled (unlike throttle governing).

Why others are incorrect

• Pressure variation is characteristic of throttle governing, not cut-off governing.
• Temperature is not the control variable; it is a function of boiler/superheater operation.

Key takeaway
Cut-off governing controls engine power by metering steam quantity (admission duration), not by throttling pressure.