Final answer:
The vacuum gauge should be connected at the low-pressure side of the system in order to measure the vacuum accurately.
Step-by-step explanation:
When measuring a vacuum of the system, the vacuum gauge should be connected at the low-pressure side. This is because a vacuum gauge is designed to measure pressures that are lower than atmospheric pressure. In a system such as a vacuum chamber used in physics experiments, the pressure inside the chamber is less than atmospheric pressure, and hence, the gauge reads a negative value. Connecting the gauge to the low-pressure side allows it to accurately measure the reduced pressure or vacuum level within the system.