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Question
what is the charge of the earth??
is it positive or negative, and why?

thank you for  your answer

Answer
Near the surface of the Earth the electric field is directed towards the Earth with an intensity somewhere in the range of 100-150N/C [It varies with location and altitude.]. If we take the average value to be 130N/C and then use Coulomb's Law we can determine the average net charge of the Earth:
E=k*q/R^2
Where R=6.37x10^6m is the radius of the Earth and k=9.0x10^9Nm^2/C^2 is the Coulomb's Law constant.
From this one can determine the average charge of the Earth to be:
q=E*R^2/k=-130*(6.37x10^6)^2/9x10^9=-5.9x10^5C
The charge is negative because the field is directed downward, towards the Earth.

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James J. Kovalcin

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I am teaching or have taught AP physics B and C [calculus based mechanics & electricity and magnetism] as well as Lab Physics for college bound students. I have a BS in Physics from the University of Pittsburgh and a Master of Arts in Teaching from same. I have been teaching physics for 34 years. I am constantly updating my skills and have a particular interest in modern physics topics.

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