# Excess or deficit electrons.

1. Oct 28, 2013

### Zondrina

1. The problem statement, all variables and given/known data

A small plastic sphere is suspended between two parallel plates like so: http://gyazo.com/0b5425a78b645d85da0b3475d6d71734

How many excess or deficit electrons does the sphere have?

2. Relevant equations

$m=2.60x10^{-15}kg$
$V=265.4V$
$d=0.500cm=0.000500m=5.0x10^{-4}m$
$g=9.81m/s^2$

$q = \frac{mgd}{V}$

$q = Ne$
$e = 1.6x10^{-19}C$

3. The attempt at a solution

The charge on the sphere is clearly positive because it is suspended in mid air and I calculated the magnitude of the charge to be $q=4.8x10^{-20}C$.

This confused me slightly. Solving for the excess/deficit electrons $N = 0.3$.

How can the sphere have a fraction of a deficit of electrons? I thought $N$ could only be an integer.

2. Oct 28, 2013

### Staff: Mentor

Check your conversion of d to meters.

3. Oct 28, 2013

### Zondrina

Whoops, I forgot a zero there $d = 5.00x10^{-4}m$.

This doesn't really change the answer though.

EDIT : Ohhh I have an extra zero -facepalm-

I got it now thanks!

4. Oct 28, 2013