NEIEP Mechanics Practice Exam

The data 120 NC 8 on a bi-metallic timer indicates what features?

1. 12 seconds timer with normally closed contacts at 120 volts

2. 8 seconds timer with normally open contacts at 120 volts

3. 8 seconds timer with normally closed contacts at 120 volts

4. 120 seconds timer with normally closed contacts at 80 volts

The correct answer is: 8 seconds timer with normally closed contacts at 120 volts

The indication of 120 NC 8 on a bi-metallic timer reveals specific features regarding its operation and purpose. The first part, "120," signifies the operating voltage of the timer, which is 120 volts. This detail is crucial because it tells us the electrical requirements for the timer to function correctly within a circuit. The "NC" refers to normally closed contacts. This means that when the timer is not active, the contacts remain closed, allowing current to flow through. When the timer is activated, the contacts open, interrupting the current. Understanding the nature of the contacts is important for circuit design and safety since it determines how the timer interacts with connected devices under different conditions. The "8" represents the timer's duration, indicating that it is designed to hold for 8 seconds before switching states (from closed to open). This timing aspect is essential for determining how long a device will be powered or how long a certain process will last. Therefore, the correct interpretation of the data 120 NC 8 leads to the conclusion that the timer operates at 120 volts, has normally closed contacts, and has an operational duration of 8 seconds.