What is an electrical variac used for?

A variac, or variable autotransformer, is specifically designed to adjust the output voltage to a desired level, making it particularly useful in electrical testing and applications where precise voltage control is required. By varying the position of the wiper on the coil of the autotransformer, users can achieve a range of output voltages from a given input voltage. This function is crucial for testing equipment and devices under different voltage conditions without the need for multiple power supplies or fixed transformers.

In contrast, measuring electrical resistance involves using a different type of instrument, typically a multimeter or ohmmeter, which is designed specifically for that purpose. As for converting DC voltage to AC voltage, that is the role of a different device known as an inverter. Lastly, while isolating circuits during testing is important for safety and preventing interference, a variac does not serve that purpose directly; it is mainly focused on voltage adjustment. Thus, the role of a variac as a tool for adjusting output voltage makes it an invaluable instrument in electrical testing environments.