Maximum charge on a green pea before sparking in dry air

[cky_uk]

I don't have a clue on where to start this as i don't 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?

 

[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.

 

[cky_uk]

any further help on this?

 

[Chi Meson]

Do you have a textbook?

 

[cky_uk]

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

 

[Astronuc]

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?

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

 

[cky_uk]

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