Final answer:
To balance electric and gravitational forces on a particle in an electric field, excess electrons are needed to achieve equilibrium.
Explanation:
To balance the electric and gravitational forces on a particle of 20 mg in an electric field of 2000 N/C,
we need to calculate the excess electrons needed to achieve equilibrium.
The gravitational force is given by weight and the electric force by the charge of the excess electrons.
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