91Ó°ÊÓ

The given data can be listed below,

• The radius of metal disk is,R=1.1 m
• The distance between two disk is,d=1.2mm
• The maximum electric field of air is, $E=3×{10}^8\mathrm{N}/\mathrm{C}$

A parallel plate capacitor is made up of two big planar parallel conducting plates separated by a tiny distance, each of which is linked to wires that are separated from one another by a thin area that can be a vacuum or a dielectric substance but not a conductor.

The electric field of capacitor is given by,

$E=\frac{Q}{2{\mathrm{Î\mu }}_0}$

Here, q is the charge on the disk, A is the area of disk and${\mathrm{Î\mu }}_0$ is the permittivity of free space.

Substitute all the values in the above equation, the charge on the disk is given by,

$$\begin{gathered} Q=EA{\mathrm{Î\mu }}_0 \\ =\left(3×{10}^6\mathrm{N}/\mathrm{C}\right)\mathrm{Ï€}{\left(1.1\mathrm{m}\right)}^2\left(8.85×{10}^{-12}{C}^2/N.{\mathrm{m}}^2\right) \\ =1.009×{10}^{-4}\mathrm{C} \end{gathered}$$

Thus, the value of Q at which spark appear between disks is $1.009×{10}^{-4}\mathrm{C}$.