What is the resistance between neutral and ground or earth?

I am an electrical engineer and here is my attempt at answering your question. Let me know if you understand this or have any follow-up questions.

The question about the resistance between the neutral and the ground (or earth) in an electrical system is an interesting one.

It's important to note that the specific value can depend on many factors including the quality of the wiring, connections, the presence of electrical noise, etc.

However, to start, let's first understand the concepts of Neutral, Ground and Earth in the context of power systems.

1. Neutral: This is typically the return path for current in an AC system. In a perfectly balanced system, the neutral carries no current. However, in practice, especially in residential settings, the loads are rarely perfectly balanced so the neutral will carry the unbalanced current.

2. Ground (Earth): Grounding or Earthing is a safety measure that directs the electric current into the earth in the case of a short circuit. This is a protective measure, designed to prevent dangerous scenarios where an electrical system fault could result in the casing or external parts of appliances becoming live with electrical energy.

Under normal operating conditions, in a correctly installed electrical system, the neutral and ground are usually at very nearly the same potential, because they are both connected to the same physical point at the electrical panel for a building.

This point is then connected to the physical earth via an 'earth grounding electrode' which is often a metal rod driven into the earth.

Let's now return to the question about resistance.

The ideal theoretical resistance between neutral and ground (earth) should be close to zero (0) ohms, because they're connected at the ground-neutral bar inside the electrical panel. However, real-world factors can increase this.

In reality, because of wire resistance, connection resistance, and other minor factors, there might be a very small amount of resistance measurable between the neutral and ground wires.

This would likely be a fraction of an ohm, assuming a properly installed and functioning system.

It's also important to note that resistance could potentially increase due to a variety of problems:

1. Poor connections: If there is corrosion, dirt, or other obstructions at the point where wires connect, it can create resistance. This is often an issue at the ground-neutral bar in the electrical panel.

2. Wire damage or deterioration: Over time, wires can become damaged or worn, creating additional resistance.

3. Long wire runs: The longer the wire, the higher the resistance. If the neutral and ground wires have to travel a long way from the panel, the resistance can be greater.

Remember, high resistance between neutral and ground in a properly functioning system can be a sign of a problem and should be investigated by a qualified electrician.

A substantial difference in potential between neutral and ground can also pose a risk of electric shock, so it's crucial to make sure the electrical system is correctly installed and maintained.

Additionally, in certain specialised circumstances (like in an isolated ground system), the neutral and ground might intentionally not be connected together at the outlet, in which case the resistance between them could be very high. But that's a more specific scenario that wouldn't typically be encountered in most residential or general commercial wiring.

Lastly, electrical codes and their interpretation can vary by country, state, and even local jurisdictions.