Power Transmission by Shafts:
The major purpose of a shaft is to transmit power from the source to driver machines in factories & workshops. Power refers to the time rate of doing work.
Let a shaft of diameter, d, subjected to torque, T, while the shaft is rotating at N rpm or ω rad/S, subjected to end couples that cause turning effect.
∴ Work done in revolution = 2π T
Work per minute = 2π N T
Power transmitted = 2π N T/60 = T ω
In general, the torque is defined in units of Nm and power in units of Watt (W) where 1 W is equal to 1 J of work per S.