A universal motor is a type of electric motor that can operate on either AC or DC supply. It is lightweight, compact, and capable of running at very high speeds, making it ideal for portable household appliances.
Hair Dryer: Uses a universal motor because it requires high-speed rotation to generate airflow and heat quickly.
Room Cooler, Refrigerator: These use induction motors which are quieter and more energy efficient for continuous operation.
Lathe Machine: Typically uses heavier-duty motors like DC shunt or induction motors due to torque requirements.
Hence, the correct answer is (A) Hair dryer.