A small drop of water is suspended motionless in air by auniform electric field
ID: 1738409 • Letter: A
Question
A small drop of water is suspended motionless in air by auniform electric field that is directed upward and has a magnitudeof 8480 N/C. the mass of the water drop is 3.50e-9 kg.(a) Is the excess charge on the water drop poistive or negative?Why? (b) How many excess electrons or protons reside on thedrop? A small drop of water is suspended motionless in air by auniform electric field that is directed upward and has a magnitudeof 8480 N/C. the mass of the water drop is 3.50e-9 kg.(a) Is the excess charge on the water drop poistive or negative?Why? (b) How many excess electrons or protons reside on thedrop?Explanation / Answer
(a) as the net force on the droplet is zero, andthe weight of magnitude W points downward, the electric force ofmagnitudemust point upward. Since the electric fieldpoints upward, the excess charge on the droplet must bepositive in order for
the force F to point upward. (b) here we use m g = E q the magnitude of the excess charge on thedroplet is |q| = m g / E = ......... C (q) (1 proton / 1.602 x 10-19 C) =.......... protons (b) here we use m g = E q the magnitude of the excess charge on thedroplet is |q| = m g / E = ......... C (q) (1 proton / 1.602 x 10-19 C) =.......... protons