Why are we not allowed to measure voltage from the neutral wire to the ground wire in an electrical wiring system?
When measuring voltage in an electrical wiring system, it is **not recommended** to measure voltage from the neutral wire to the ground wire.
This is because the neutral wire is **not** always at zero potential with respect to the ground wire ¹.
The neutral wire is tied to a potential of 0V in comparison to ground with a very low resistance.
This means, that high currents can flow through the neutral wire without any noticeable voltage appearing on the neutral wire ².
If you measure voltage between the neutral and ground wires, you may get a reading that is not accurate and could be dangerous.
It is recommended to measure voltage between the hot wire and either the neutral or ground wire.