If the surface of the earth is negatively charged why do electrons move towards the earth when a negatively charged conductor is being discharged via earthing?
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2$\begingroup$ Why do you think earth is negatively charged? $\endgroup$– NephenteCommented Aug 6, 2019 at 10:20
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$\begingroup$ physics.stackexchange.com/q/3955/25301 $\endgroup$– Kyle KanosCommented Aug 6, 2019 at 11:39
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1 Answer
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The earth is negatively charged relative to its upper atmosphere, which is positively charged per Kyle Kanos' link above. But all the electrons flowing around near the surface of the earth are unaffected by the net charge of the earth. Here is how to understand this:
Imagine we construct a circuit like a digital clock on a PC board and power it with a battery. But just for safety we also connect the negative battery terminal to an earth ground. The circuit works fine.
Now we replace the ground connection with a battery of voltage V whose negative terminal is connected to earth ground and whose positive terminal is connected to the negative battery terminal of the circuit. We have now lifted the ground reference of our circuit to a voltage that is +V volts above ground. We notice that the circuit still works fine.
This means that we can designate our ground reference to be any voltage we want- because the thing that drives the electrical circuit is voltage differences, and these are unaffected by any DC bias that the ground reference may possess.
answered Aug 6, 2019 at 16:19