Option 1: D.C. shunt motor
Option 2: Synchronous motor
Option 3: Induction motor
Option 4: D.C. compound motor
Correct Option: 2
Explanation
The correct answer is option 2, which is a synchronous motor. A synchronous motor rotates at a synchronous speed due to interlocking of stator R.M.F poles and rotor poles. The speed of DC shunt motor and DC compound motor can be changed by varying the back emf and flux. The speed of the Induction motor can be varied by varying the slip, number of poles, or frequency of the supply. The synchronous speed formula is Ns = 120f/P.