Why short circuiting rings are used in squirrel cage motor?

Squirrel Cage motor is a kind of Induction Motor. The reason an induction motor sometimes refered to a rotating transformer is because the stator (Primary windings in a transformer), which is powered to set up a magnetic field induces a current in the armature coils (secondar coils in a transformer). However, instead of giving an electrical power output, the coil is short circuited to produce mechanical output (torque in this case)