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The direction of rotation of universal motor can be reversed the by reversing the flow of current through
Armature winding
Field winding
Either Armature or Field
both of the winding
Either Armature or Field
Quick Trick: The direction of torque in a DC series or universal motor depends on the relative polarity between the armature and field; reversing only one reverses torque, but reversing both leaves direction unchanged.
The direction of torque in a DC series or universal motor depends on the relative polarity between the armature and field; reversing only one reverses torque, but reversing both leaves direction unchanged.
Analyze Torque Production Mechanism
In a universal motor (DC series motor operating on AC or DC), torque is developed due to the interaction between field flux and armature current (Torque is proportional to Field Flux times Armature Current).
Evaluate Reversal of Current Flow
To reverse the direction of rotation (torque), you must reverse the direction of current flowing through either the armature winding OR the field winding, which changes the relative magnetic field relationship.
Understand Reversing Both Windings
If you reverse current through both windings simultaneously (such as during normal AC supply alternation), the negative signs cancel out ((-Field) x (-Armature) = +Torque), maintaining rotation in the same direction.
A: Incomplete, because changing field winding alone also reverses direction. B: Incomplete, because changing armature winding alone also reverses direction. D: Incorrect, because reversing both simultaneously results in the motor rotating in the same original direction.
C is correct because reversing the current in either the armature or the field winding alters the relative magnetic polarity, which reverses the motor's direction of rotation.
Common trap: AC supply naturally reverses current in both windings simultaneously every half cycle, which is why universal motors continue running in ONE direction on AC supply.