# Homework Help: Green Pea Discharge

1. Aug 13, 2006

### cky_uk

I dont have a clue on where to start this as i dont know what other figures to use.

Dry air will break down and generate a spark if the electric field exceeds 3x106N/C. How much charge could be packed onto a green pea (diameter 0.75cm) before the pea spontaneously discharges?

2. Aug 13, 2006

### Chi Meson

This is a quaestion about capacitance. You need to find how the capacitance of a single object (as opposed to parallel plates) is related to its surface area.

3. Aug 13, 2006

### cky_uk

any further help on this?

4. Aug 13, 2006

### Chi Meson

Do you have a textbook?

5. Aug 13, 2006

### cky_uk

no i dont,could you possible give me the equation?

6. Aug 13, 2006

### Astronuc

Staff Emeritus
One has to calculate the charge that yields an electric field of 3x106 N/C on a sphere of diameter 0.75 cm.

Then one should know the equation for the electric field at the surface of a sphere. This is an application of Gauss's Law. See - hyperphysics.phy-astr.gsu.edu/Hbase/electric/elesph.html (unfortunately site is down at the moment).

Also -
http://physics.bu.edu/~duffy/PY106/Electricfield.html (toward bottom of page),

Worked example 4: Electric field of a uniformly charged sphere
http://farside.ph.utexas.edu/teaching/302l/lectures/node18.html

7. Aug 13, 2006

### cky_uk

thank you for your help,are you any good with biology equations?