72 - Electricity Questions Answers

All options are dimensionally incorrect. Please rectify.

See the clip

Let potential of a disc of radius x is V. For this, see video given below

Now potential energy of this disc with a circular layer of charge$$\begin{gathered} 2\mathrm{\pi xdx\sigma } \mathrm{is} \mathrm{V}2\mathrm{\pi xdx\sigma } \\ \mathrm{put} \mathrm{the} \mathrm{value} \mathrm{of} \mathrm{V} \mathrm{and} \mathrm{integrate} \\ \mathrm{inform} \mathrm{for} \mathrm{any} \mathrm{problem} \end{gathered}$$ 

$$\begin{gathered} We know that \\ \sum _{plane}EdS\cos \theta = \frac{q}{6{\epsilon }_0} \left(1\right) \\ and Net force on the plane =\sum _{plane}{F}_{\perp }dQ \\ =\sum _{plane} qE\cos \theta dS\sigma =\frac{Q}{d^2}\sum _{plane} qE\cos \theta dS \left(2\right) \\ Now solve eq. \left(1\right)\hspace{0.17em}and \left(2\right) \end{gathered}$$