Radius \(r =0.5 \,mm =5 \times 10^{-4}\, m\)

\(E =10 \times 10^{-3}\, \frac{ V }{ m }\)

\(J =\sigma E =10 \times 10^{-3} \times 5 \times 10^{7}\)

\(J =5 \times 10^{5}\)

\(\frac{ i }{ A }=5 \times 10^{5}\)

\(i =5 \times 10^{5} \times \pi r ^{2}\)

\(=5 \times 10^{5} \times \pi \times\left(5 \times 10^{-4}\right)^{2}\)

\(=125 \pi \times 10^{-3} \,Amp\)

\(i=125 \pi \, mA\)

\(x=5\)