How Much Voltage Is Needed to Suspend Charged Water Droplets?

[Chawker]

Homework Statement

You intend to suspend water droplets in mid-air to understand rainfall.

You give the droplets a small positive charge, and keep them suspended by an electric field upwards.

The experiment consists of two horizontal metal plates, separated by 9.3m. The water droplets have a mass of 2.8 * 10^-9 kg and have a charge of 6.4*10^-10 C

What voltage should you supply to keep them hovering?

Homework Equations

V = E/d
E=kq/r^2[/B]

The Attempt at a Solution

Kind of lost on this one. I thought about using e=kq/r^2 with the given information then substituting it into the first equation however that still doesn't include the mass component of the question, even if its needed at all.

How should i go about this problem?

 

[BvU]

Hello Chawker,

V = e/d

In turn, I am lost on this one. You could have avoided that by listing your variable names in part 1 (e = electric field strength ? In physics e is electron charge) Then your eqn doesn't fly dimensonally at all. Where does it come from ?

separated by 9.3m

big experiment ?

Your elevant equations set is incomplete: they do not feature the mass at all.

 

[PumpkinCougar95]

For drops to hover the Electric force $F = Eq$ must balance the gravitational force $F=mg$. What is the E field?

Edit: $E = \frac{Kq}{r^2}$ is for point charges. What kind of Electric field is there between two charged plates ?

 

[BvU]

two horizontal metal plates

form a capacitor

 

[Chawker]

For drops to hover the Electric force $F = Eq$ must balance the gravitational force $F=mg$. What is the E field?

Edit: $E = \frac{Kq}{r^2}$ is for point charges. What kind of Electric field is there between two charged plates ?

So we're looking at Eq = mg then solving v = E *d?

EDIT : Figured it out, thanks for the help guys!

 

[BvU]

You're welcome