# Homework Help: Radius of a Raindrop given Charge and Electric Potential

1. Jul 15, 2013

### freddy13

1. The problem statement, all variables and given/known data
A spherical rain drop carries a charge of 5×10-6 C and has a potential of 8.800×10-8 V at the surface. Find the radius of the drop.

2. Relevant equations

V = (kQ)/r

3. The attempt at a solution

I simply moved V and r to their respective spots and plugged in my numbers. I got a very large number of 5.11*10^11, so i am wondering if my units are wrong or if I am doing something else wrong. Thanks for your help!

2. Jul 16, 2013

### TSny

Hello, freddy13.

You're right, you're getting a ridiculous answer even though your method is correct. (Your answer for the radius is more than 3 times the distance to the sun.) The value for the potential looks very suspicious. Are you sure that 10 is raised to the negative 8 power? Also, the value for the charge seems very high for a raindrop.

Last edited: Jul 16, 2013
3. Jul 16, 2013

### freddy13

Yeah I copied the problem exactly! It has to be something with the units that I am missing, that seems to be the only possibility!

4. Jul 16, 2013

### TSny

I agree. It must be a misprint in the statement of the problem.