Answer:
[tex]E=1.81\times 10^5\ N/C[/tex]
Explanation:
In Millikan oil drop experiment, oil drops were suspended against the gravitational force by a vertical electric field such that its weight is balanced by the electron force i.e.
W = qE,
W is weight, W = mg
q is charge,
E is electric field
⇒ [tex]2.9\times 10^{-14}\ N=qE[/tex]
or
[tex]E=\dfrac{2.9\times 10^{-14}\ N}{1.6\times 10^{-19}\ C}\\\\E=181250\ N/C\\\\\text{or}\\\\E=1.81\times 10^5\ N/C[/tex]
So, the magnitude of the electric field is [tex]1.81\times 10^5\ N/C[/tex].