A fan operates at 200 volt (DC) consuming $1000W$ when running  at full speed. It’s internal wiring has resistance $1\Omega$ .  When the fan runs at full speed ,its speed becomes constant. This is because the torque due to magnetic field inside the fan is balanced by the torque due to air friction between the fixed part and the shaft of the fan. The electrical power going into the fan is spent (i) in the internal resistance as heat, call it  $P_1$  (ii) in doing work against internal friction and air resistance producing heat, sound etc. call it  $P_2$. When the coil of fan rotates, an emf is also induced in the coil. This opposes the external emf applied to send the current into the fan. This emf is called back – emf , call it ‘ $e$’.