- #1
fluidistic
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Homework Statement
The electric field on the Earth' surface is not null. Assume that the intensity of the field on Earth' surface is 300 N/C pointing in Earth's center. Calculate the excess of charges in Earth' surface giving the result in terms of electrons per [tex]m^2[/tex].
Homework Equations
Don't know.
The Attempt at a Solution
I'm stuck at starting the problem. How can the electric field point in Earth's center? Charges must be at the surface so I've no clue about the direction of the field.
I also do not have any idea about which formula to use.
Maybe [tex]E=A \cdot \sigma[/tex]? So [tex]4 \pi r^2 \sigma= \frac{300N}{C} \Rightarrow \sigma =\frac{100}{6300^2 \cdot \pi}[/tex]. But a dimensional analysis shows that I'm wrong. I get that the units of this are [tex]\frac{kg}{s^2Cm}[/tex] which clearly isn't a surface charge density. (I should get [tex]\frac{C}{m^2}[/tex] I guess.)