Quiet@Remove["Global`*"];

Quiet@<<PhysicalConstants`

μ0=(VacuumPermeability//N)[[1]]
(*VacuumPermittivity//N*)

(Sqrt[(2/(ω*γ*μ))])/.{ω->2*Pi*50.,γ->57*(10^6),μ->μ0}

curl[vect_]:=Curl[vect, {r,θ,z}, "Cylindrical"]

Evect={0,0,Ez[r]};
Hvect={0,Hfi[r],0};
eqn1=Thread[curl[Evect]==-I*ω*μ*Hvect][[2]];
eqn2=Thread[curl[Hvect]==γ*Evect][[-1]];
sol=(DSolve[{eqn1,eqn2},{Ez[r],Hfi[r]},r][[1]]//Simplify[#,{ω>0,γ>0,μ>0.}]&)/.C[2]->0

(((-1))^(3/4))//ComplexExpand

Jzobecne[r_]=BesselJ[0,-(1-I)* (r/a) ] C[1]*γ

proud=Integrate[2*r*Pi*Jzobecne[r],{r,0,rmax}]

J[r]

J[r_]=Jzobecne[r]/.Solve[proud==Icelkovy,C[1] ][[1]]//FullSimplify;

Abs[J[r]/.dos]

dos={a->0.00942,Icelkovy->1,rmax->0.04};
Plot[Abs[J[r]/.dos],{r,0,rmax/.dos},AxesLabel->{"r [m]","Abs[J] [A/(m^2)]"},GridLines->Automatic,PlotStyle->{Red,Thick},AxesOrigin->{0,0},PlotRange->All]

ClearAll[Pztraty]
Pztraty[rmaxx_]:=Module[{dos={a->0.00942,Icelkovy->1,γ->57*(10^6),delka->1},jecko},
jecko=J[r]/.dos/.rmax->rmaxx;
delka*2*(Pi/γ)*NIntegrate[r*((Abs[jecko])^2),{r,0,rmaxx}]/.dos

];
Pztraty[0.001]

dos={a->0.00942,Icelkovy->1,γ->57*(10^6),delka->1};

RkuRhomogenni[rmax_]:=((Pztraty[rmax])/(1/(γ*Pi*(rmax^2))))/.dos;
RkuRTrubka[rmax_]:=((Pztraty[rmax])/(1/(γ*Pi*((rmax^2)-(((rmax-a))^2)))))/.dos;

{#,RkuRhomogenni[#]}&/@Range[0.00001,0.02,0.001];
ListPlot[%]

{#,RkuRTrubka[#]}&/@Range[0.02,0.1,0.01];
ListPlot[%]