Question

Delicate measurements indicate that the Earth has an electric field surrounding it, similar to that around a positively charged sphere. Its magnitude at the surface of the Earth is about 100 N/C. What charge would an oil drop of mass 2.0 x 10 15 kg have to have, in order to remain suspended by the Earth’s electric field? Give your answer in Coulombs ?

Answer 1

Answer:

q = 1.96 10⁴ C

Explanation:

The elective force is given by

         $F_{e}$ = q E

Where E is the electric field and q the charge.

Let's use Newton's law of equilibrium for the case of the suspended drop

               F_{e} –W = 0

               F_{e} = W

               q E = m g

               q = m g / E

Let's calculate

              q = 2.0 10⁵ 9.8 / 100

              q = 1.96 10⁴ C