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The radius of plates, $R=30\mathrm{mm}=0.03\mathrm{m}$

Plate separation, $d=0.005\mathrm{m}$

Maximum potential difference, $V=150\mathrm{V}$

Frequency, $f=60\mathrm{Hz}$

$V=\left(150\right)\sin \left[2蟺\left(60\mathrm{Hz}\right)t\right]$

By using the Maxwell equation, finding the magnetic field for the maximum potential, and plotting the graph maximum Bvs rMaxwell's equations represent one of the most elegant and concise ways to state the fundamentals of electricity and magnetism.

Maxwell鈥檚 law of Induction-

$.\stackrel{鈫�}{B}.d\stackrel{鈫�}{A}={渭}_0{\mathcal{E}}_{0}A\frac{dE}{dt}$

The electric field is given as-

$E=\frac{V}{d}$

Where, B is the magnetic field,is the area enclosed by the Amperianloop,Eisthe electric field, t is the time, Vis the potential difference and, dis the distance.

The electric field is given as-

$E=\frac{V}{d}$

The magnetic field induced by the changing electric field is given by the relation,

localid="1663162361810" style="max-width: none; vertical-align: -15px;" $\stackrel{鈫�}{B}.d\stackrel{鈫�}{A}={渭}_0{\mathcal{E}}_{0}A\frac{dE}{dt}$

Where,localid="1663162418635" $A$is the area enclosed by the Amperian loop, which is, localid="1663162390281" $A=蟺d^2$.

So that, for $r<R$,

$\begin{array}{rcl}B\left(2蟺r\right)& =& {渭}_0{\mathcal{E}}_0蟺r^2\frac{dE}{dt}\\ B& =& \frac{{渭}_0{\mathcal{E}}_{0}r}{2}\frac{dE}{dt}\end{array}$

But,

$E=\frac{V}{d}$

So,

$\begin{array}{rcl}B& =& \frac{{渭}_0{\mathcal{E}}_{0}r}{2d}\frac{dV}{dt}\\ B& =& \frac{{渭}_0{\mathcal{E}}_{0}r}{2d}\frac{d}{dt}\left(V_{max}\sin 蝇t\right)\\ B& =& \frac{{渭}_0{\mathcal{E}}_{0}r}{2d}{V}_{max}蝇\cos 蝇t\end{array}$

For the maximum value of potential $V_{max}=150\mathrm{V}$,

$B=\frac{{渭}_0{\mathcal{E}}_{0}r}{2d}{V}_{max}蝇$

The $r=R=0.03\mathrm{m}$

localid="1663161555184" $\begin{array}{rcl}B& =& \frac{\left(4蟺脳{10}^{-7}\text{H/m}\right)\left(8.85脳{10}^{-12}\text{F/m}\right)脳0.03\text{m}}{2脳0.005\text{m}}脳150脳2蟺脳60\text{Hz}\\ B& =& 1.9脳{10}^{-12}\mathrm{T}\end{array}$

Therefore, the maximum value of the induced magnetic field that occurs at $r=R$is $B=1.9脳{10}^{-12}\mathrm{T}.$

The maximum value of $B$,the magnetic field is induced by the changing electric field so that,

$\begin{array}{rcl}{B}_{max}& =& {\left(\frac{{渭}_0{\mathcal{E}}_0{R}^2}{2r}\frac{dE}{dt}\right)}_{max}\\ B_{max}& =& {\left(\frac{{渭}_0{\mathcal{E}}_0{R}^2}{2rd}\frac{dV}{dt}\right)}_{max}\\ B_{max}& =& {\left(\frac{{渭}_0{\mathcal{E}}_0{R}^2}{2rd}{V}_{max}蝇\cos 蝇t\right)}_{max}\\ B_{max}& =& {\left(\frac{{渭}_0{\mathcal{E}}_0{R}^2}{2rd}{V}_{max}蝇\right)}_{max}\end{array}$

So, all values are constant except r.

B is dependent on the value of r, so plot the graph B vs r.

$\begin{array}{rcl}{B}_{max}& =& \frac{\left(4蟺脳{10}^{-7}\text{H/m}\right)\left(8.85脳{10}^{-12}\text{F/m}\right)脳{\left(0.03\text{m}\right)}^2}{2脳0.005\text{尘脳谤}}脳150脳2蟺脳60\text{Hz}\\ & =& 5.7脳{10}^{-14}脳\frac{1}{r}\end{array}$

Here, r varies from 0 to 0.1.

Hence, plotted the graph $B_{max}$vs $r$, for varying from 0 to 0.1.