In a universal motor, the most common cause of brush sparking is open armature winding, shorted armature winding, shorted field winding, high commutator mica.
Answer : The speed of a universal motor is usually reduced by using gearing.
Answer : Speed control of a universal motor is achieved by varying field flux with tapped field windings, connecting rheostat in series, applying variable voltage by means of silicon controlled rectifier, applying variable voltage by means of variable auto-transformer.
Answer : A universal motor is one which can be operated either on D.C. or A.C. supply at approximately the same speed and output.
Answer : The speed/load characteristics of a universal motor is same as that of D.C. series motor.
Answer : The speed control of universal motor used for sewing machines is by varying the resistance.