• Various definitions exist in terms of enthalpies, pressures or flow geometry of the device.
• In case of turbines, both impulse and reaction machines, degree of reaction (R) is defined as the ratio of energy transfer by the change in static head to the total energy transfer in the rotor i.e.

• For a gas turbine or compressor it is defined as the ratio of isentropic heat drop in the moving blades (i.e. the rotor) to the sum of the isentropic heat drops in the fixed blades (i.e. the stator) and the moving blades i.e.

Hence, the correct option is (B).