Which of the following motors is characterized as a universal motor?

A universal motor is defined as a type of motor that can operate on either AC or DC power. This unique characteristic makes it versatile and widely used in applications like power tools and household appliances. The series motor is the correct answer because it is designed in such a way that the field winding is connected in series with the armature winding.

When this motor operates on DC supply, it can produce high starting torque and a wide speed range. Under AC supply, the same construction allows it to function efficiently as well. This dual capability aligns perfectly with the definition of a universal motor.

In contrast, other motor types such as a shunt DC motor, capacitor motor, and induction motor have specific operational limitations. The shunt DC motor primarily runs on direct current, and while it can be modified for AC, it is not inherently designed for it. Both the capacitor motor and the induction motor primarily operate on alternating current, making them unsuitable for defining a universal motor.