Make sure electro does not fall

[seto6]

THIS IS NOT A HOME WORK QUESTION THIS AS FROM ANOTHER Tutorial

find the electric field E need to prevent an electron from falling down to ground, when close to surface of the earth.

i approached this question saying that take gravity into account and take Earth to be negatively charged.

then Fg=Eq then Fg/q=E...

mg/q=E

is this correct?

if not can you explain the reasoning please!

 

[Doc Al]

Looks good to me.

 

[seto6]

normally do we take Earth to be + or negative?

 

[Doc Al]

normally do we take Earth to be + or negative?

The electric field surrounding the Earth points downward. (The Earth is negatively charged.)

 

[seto6]

thanks that makes more sense now!