Final answer:
After the centrifugal switch operates in a resistance split phase motor, the cross field effect simulates a single-phase induction motor. Back emf is induced as the motor rotor turns, opposing the driving emf and thus stabilizing the current draw to prevent overheating.
Step-by-step explanation:
When discussing the behavior of a resistance split phase motor that is running, specifically after the centrifugal switch has operated, it is important to understand the role of the back emf (electromotive force). When a motor spins, a rotating coil will have an induced emf; this phenomenon opposes the input emf to the motor. Once the centrifugal switch has activated and disconnected the start winding from the circuit, the motor continues to run only on the run winding. The cross field effect creates conditions similar to a single-phase induction motor, where a single alternating current induces a magnetic field that ultimately turns the rotor. In a resistance split phase motor, as the rotor accelerates and the back emf increases, it opposes the driving emf, thereby stabilizing the current the motor draws. This condition helps protect the motor from drawing too much current and prevents it from overheating and potentially burning out. The back emf plays a crucial role in maintaining efficient operation and allows the motor to perform the necessary mechanical work with a stable current draw, thereby simulating the characteristics of a single-phase induction motor. Overall, understanding the relationship between the back emf and the operation of an electric motor is essential in applications such as powering appliances or industrial equipment where efficient and reliable operation is critical.