When testing a transformer, what does a reading of "open" indicate?

A reading of "open" when testing a transformer indicates that there is a break in the circuit, which implies that the transformer is faulty. This condition means that electrical current cannot flow through the transformer due to an interruption, which could be caused by a variety of issues, such as internal damage or an external connection failure. Essentially, the "open" reading signifies that the transformer is not performing its intended function of transferring electrical energy between circuits, confirming that it is not operational.

In this context, other options such as the transformer being operational, new, or fully functional would not match the situation indicated by an "open" reading, as these conditions would require the transformer to actively conduct electricity.