SOLUTION

• If field winding is reversed then the current flowing through the field winding reverses so the effective flux will be reversed. we know that Torque is proportional to flux.
• As there is a reversal of flux i.e. from positive it becomes negative so torque generated also becomes negative resulting motor rotating in the reverse direction.
• Note: To reverse the motor, you need to change the polarity of the supply voltage to either the field winding or the armature winding, but not both.