Electric fields (earth) questions URGENT - 10 pts?

Question

I have this question on an exam in an hour lol.

The earth has an electric field of 1 x 10^2 N/C at its surface pointing towards the centre.

a) a uniformly charged sphere produces and electric field outside the object exactly the same as the field that would be produced if the charge was concentrated at the centre of the field. assume the earth is uniformly charged. what is the type and magnitude of the charge of the earth?

b)compare the earth's electric field and gravitational field in terms of (i) direction and shape, (ii)effects on objects and (iii) how it changes as height increases

c)what is the largest mass that can be suspended by the electric field of earth if the particle has the elementary charge on it?

d)could the electric field of earth be used to suspend (i) a proton and (ii) an electron? explain

THANK YOU IN ADV :)

Answer 1

Using Coulombs Law, the charge would be

Q = (1 X 10^2) * (6.36 X 10^6)^2 * 4 * pi *  (8.854X10^-12)

= 4.50 X 10^5 Coulombs

i) Direction and Shape are the same, both are pointed toward the center

ii) Gravity attracts all masses, the electric field will attract or or repel depending on the charge on the object.  If the net charge on an object is zero then the electric field will not produce a force.

iii) Both the gravitational field and electric field decrease as 1/r^2

c) I will let you look up the equations and calculate that one yourself - see the Wikipedia Articles

d) Obviously the Electric field cannot suspend both a proton and electron, one will be repelled (suspended) and the other will be attracted.