Physics paralell-plate capacitor?

Question

Air breaks down when the Electric field strength reaches 3*10^6 N/C causing a spark. A parallel-plate capacitor is made from two 4.0cm diameter disks how many electrons must be transferred from one disk to the other to create a spark between the disks.
I have figured out the charge Q=33.4nC but how do i find out the amount of electrons transferred?

Answer 1

Diameter of the ,d = 4 cm

                                  = 0.04 m

Charge,q=33.4 nC

                =33.4n C

Electric field strength,E =3*10^6 N/C

----------------------------------

We have that E = σ/εo

                            = Q/(A*εo)

                        Q=EAεo

                            = E( (π/4)*d^2*εo)

                             =3*10^6*(π/4)*0.04^2*8.854x10^-12

                             =3.338*10^-7  C

Number of electrons,n=33.4/3.338*10^-7

                                         =10^8  electrons

Number of electrons transferred are 10^8 electrons