Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.
Trending News
How many electrons would one grain have to pick up?
Much of the material making up Saturn's rings is in the form of tiny dust grains having radii on the order of 10^-6 m. These grains are located in a region containing a dilute ionized gas, and they pick up excess electrons. As an approximation, sup-pose each grain is spherical, with radius R=1.0x10^-6 m. How many electrons would one grain have to pick up to have a poten-tial of -400 V on its surface (taking V=0 at infinity)?
1 Answer
- 9 years agoFavorite Answer
V = k*Q / R
So the required charge is
Q = V * R / k = -400 * 10^-6 / 9*10^9 = -4.4*10^-14 Coulomb
The number of electrons is N = Q / e
N = -4.4*10^-14 / -1.6*10^-19 = 278,000
or about 300,000 to 1 sig.fig.
