Final answer:
Resistance split-phase motors, which have their rotational direction fixed after starting due to an open centrifugal switch, are referred to as single-direction or non-reversible. Brushes and commutators are used to maintain torque, while back emf regulates power consumption.
Step-by-step explanation:
Once the resistance split-phase motor is started, the direction of rotation cannot be reversed because the normally closed centrifugal switch is open. As the motor reaches certain operating speeds, this switch opens, disabling the start winding and thereby fixing the rotational direction. The types of motors that operate in this manner are commonly referred to as single-direction or non-reversible motors. These motors use automatic switching mechanisms such as brushes and commutators to reverse the current every half rotation to maintain torque in a single direction. Moreover, the induced emf, also known as back emf, plays a crucial role in regulating the motor's power consumption by opposing the input emf and reducing the current draw as the motor picks up speed.