What condition indicates a normally closed pressure electric switch?

A normally closed pressure electric switch is designed to maintain a closed circuit until a specific pressure threshold is reached. When no pressure is applied, the switch remains closed, allowing current to flow through the circuit. This configuration is commonly utilized in safety and control applications, where continuous power is required until a specific condition, such as sufficient pressure, is reached.

Thus, the correct answer states that the switch is closed when pressure is applied, emphasizing the function of the switch in controlling electrical devices by responding to pressure changes in the system. This design is crucial because it ensures that the connected equipment does not operate until the pressure condition is adequate, preventing potential damage or unsafe operation.