What happens to M1 when PB is released while the control power is ON?

In a control circuit, the operation of motors like M1 is typically governed by push buttons and control relays. When PB (the push button) is pressed, it typically energizes or activates the circuit, allowing M1 to run. However, once the push button is released, the circuit may open depending on how it is designed.

If the control power remains ON when PB is released, the state of M1 will depend largely on whether any retaining circuit exists to maintain its operation after the button is released. In this scenario, the correct outcome is that M1 stops, as the action of releasing the push button would break the circuit needed for M1 to continue running. There is no sustained energizing mechanism without the push button being pressed, causing M1 to cease its operation.

Therefore, in this case, when PB is released while the control power remains ON, the motor M1 stops working because it loses the control signal that was provided by the push button, which was essential to keep it running.