# If Earth is negatively charged, then how can electrical ground be used as an electrical neutral?

According to "What is the net charge of the Earth?", the Earth is negatively charged, with a net charge of ${q}_{\small{\text{Earth}}} \approx - 5 \cdot {10}^{5} \, \mathrm{C} .$

Despite this negative charge, we still run grounding rods into the Earth to provide grounding for electrical devices.
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Question: How can electrical grounds function if the Earth already has a negative charge?

• Related, if not duplicates: Is the Earth negatively or positively charged? and What is the net charge of the Earth? – David Hammen Sep 16 '18 at 17:39
• Welcome to SE.Physics! I had a pretty hard time reading your question, though I tried to translate it. Please feel free to edit the question to better reflect your thinking if anything seems off! – Nat Sep 16 '18 at 18:46
• Charge is irrelevant. The important thing here is voltage difference. We can't actually measure voltage, just voltage difference. See Torsors made easy by John Baez. – PM 2Ring Sep 17 '18 at 18:27
• @PM2Ring You're right. "voltage difference" (or technically, potential difference) is what that is important factor here. It's like zeroing a weighing scale with a container on the scale by pressing the 'tare' button. The scale still gives correct value with or without a container, since it always measures the difference of weights. – pongapundit Jun 5 '19 at 15:13

## 2 Answers

When a conductor is grounded, its potential is equalized with the potential of the Earth and, provided that the grounding is adequate (low impedance), a large current can flow between the conductor and the ground without causing a significant potential difference between them.

This renders the conductor safe, which is the main point of the grounding.

The fact that both Earth and the grounded conductor have (the same) high potential relative to infinity or relative to the clouds or the ionosphere does not affect the effectiveness of the grounding.

The earth can be charged to any static voltage you want, positive or negative relative to outer space, and still be effective as a ground reference. This is because there is nowhere for that static bias voltage to flow to, which means it can serve perfectly well as a ground.