# 72 - Electricity Questions Answers

**Asked By: ABHISHEK**

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**Joshi sir comment**

All options are dimensionally incorrect. Please rectify.

Derive the expression or show that:Path independence of line integral of electrostatic field,, conservative nature of electrostatic force.

**Asked By: SANJAY**

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**Joshi sir comment**

See the clip

Find potential energy of disc having charge density sigma uniformly distributed on its surface,radius R

**Asked By: AKASH MAURYA**

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**Joshi sir comment**

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$2\mathrm{\pi xdx\sigma}\mathrm{is}\mathrm{V}2\mathrm{\pi xdx\sigma}\phantom{\rule{0ex}{0ex}}\mathrm{put}\mathrm{the}\mathrm{value}\mathrm{of}\mathrm{V}\mathrm{and}\mathrm{integrate}\phantom{\rule{0ex}{0ex}}\mathrm{inform}\mathrm{for}\mathrm{any}\mathrm{problem}$

**Asked By: SRIJAN**

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**Joshi sir comment**

$Weknowthat\phantom{\rule{0ex}{0ex}}\sum _{plane}EdS\mathrm{cos}\theta =\frac{q}{6{\epsilon}_{0}}\left(1\right)\phantom{\rule{0ex}{0ex}}andNetforceontheplane=\sum _{plane}{F}_{\perp}dQ\phantom{\rule{0ex}{0ex}}=\sum _{plane}qE\mathrm{cos}\theta dS\sigma =\frac{Q}{{d}^{2}}\sum _{plane}qE\mathrm{cos}\theta dS\left(2\right)\phantom{\rule{0ex}{0ex}}Nowsolveeq.\left(1\right)\hspace{0.17em}and\left(2\right)$