The classic Millikan oil drop experiment was the first to obtain an accurate measurement of the charge on an electron. In it, oil drops were suspended against the gravitational force by a vertical electric field. Given the oil drop to be 1.00 um in radius and have a density of 920 kg/m^3. a. Find the weight of the drop.
b. If the drop has a single excess electron, find the electric field strength needed to balance its weight.

a)

b)

Explanation:

a) The weight is just the mass of the drop times the acceleration of gravity.

Or in terms of density.

(1)

If we consider the volume of a drop as spherical, we can find the volume (R=1 μm = 0.000001 m).

Then, using equation (1), the weight will be:

b) To balance the weight, the electric field times the charge must be the same value in the opposite direction, which means:

I hope it helps you!

i think the answer is a and b

i wish you luck

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