what is a universal ac/dc motor
A motor which can be operated either on DC (direct current) or on single phase AC (alternating current) is called a universal motor. On both AC and DC, it gives approximately the same speed and output. Universal motors often run at dangerously high speed when operated at no load. This means that motor speed will be low at full load, but the speed of the motor will start increasing as the load on the motor decreases.