What causes contacts in a motor starter to return to their open position?

The return of contacts in a motor starter to their open position is primarily due to mechanical spring action. When the motor starter is energized, the contacts close and allow current to flow through the motor circuit. However, once the control circuit is de-energized, the mechanical springs that are part of the contact assembly play a crucial role in the operation of the starter. These springs provide the necessary force to pull the contacts apart, effectively opening the circuit and stopping the current flow.

This mechanical action is fundamental to the design of motor starters, as it ensures that the contacts do not remain closed when they are no longer required to be. The rapid release of the contacts also enhances safety by ensuring that the motor does not continue to operate unintentionally, which could lead to equipment damage or hazards. The other options do not play a role in returning contacts to their open position effectively. For instance, while electrical charge may cause the contacts to close, it does not influence their return. Similarly, heat dissipation and gravity do not have a direct effect on the mechanical operation of the contacts in this context.