Page 42 - Basic Electrical Engineering
P. 42
When a Force, F Newton acting on a body moves it in the direction of the
force by a distance d meters:
Work done = F × D Nm or Joules
When a force F Newton is applied tangentially on a rotating body making a
radius r meters, then
Work done in 1 revolution = F × 2πr (since distance moved is 2πr)
= 2πFr Nm
Force × Perpendicular distance = Torque, i.e., F × r = T
Work done in 1 revolution = 2πT Nm
∴ Work done in N revolutions/second
= 2πTN Nm
If N is expressed in revolutions per minute (rpm)
When a body of mass m kg is lifted to a height h meters against the
2
gravitational force g m/sec , work done is converted into potential energy of
the body.
Potential energy = Weight × Height
= mgh Joules. (1.16)
2
Kinetic energy of a body of mass m kg moving at a speed of v meters/sec =
Joules. (1.17)
Electrical energy
As mentioned earlier, work done in an electrical circuit is its energy.
