Answer

Series Motor (DC Series)

Components: Field winding series with armature, commutator, brushes, stator/rotor iron.

Construction: Field coil in series → same current $I_a$ flows through field and armature. Flux $\phi \propto I_a$, torque $T \propto \phi I_a \propto I_a^2$.

Working: Supply → series field → armature → torque high at low speed, speed $N \propto V/\phi$.

Advantages: Very high starting torque, suitable for traction.

Disadvantages: Speed dangerously high at no load, poor speed regulation, sparks.

Applications: Electric train, crane, hoist, starter motor.

Final: Series motor field series with armature $T\propto I_a^2$, high starting torque for traction.