Final answer:
The voltage reading indicates functional power supply, but a leak in the combustion chamber would alter the pressure in the system, likely causing it to shut down for safety. Issues with the flame sensor or cad-cell can also prevent operation.
Step-by-step explanation:
If there is a voltage reading of 120 volts across terminals BK and WH in a system with a combustion chamber, this typically indicates that the power supply to the unit is functional. However, the presence of a slight leak in the combustion chamber can be a significant issue. A leak can cause improper combustion and potentially dangerous operation, which would cause the system to not operate correctly or shut down as a safety precaution. Answer options provided suggest various issues with components like the flame sensor (FS) or the cad-cell. A defective FS or dirty or faulty cad-cell can prevent the burner from operating properly.
The ideal gas law PV = NkBT, where P is pressure, V is volume, T is temperature, kB is the Boltzmann constant, and N is the number of atoms or molecules, dictates that if the system is heated (as in the case of fuel combustion), any leak would alter the pressure and hence the operation of the system. In the context of a combustion engine, an increase in temperature due to fuel ignition should result in increased pressure; however, a leak would disrupt this process, potentially leading to a shutdown.