An electron revolves around an infinite cylindrical wire having uniform linear change density $2 \times 10^{-8} \mathrm{Cm}^{-1}$ in circular path under the influence of attractive electrostatic field as shown in the figure. The velocity of electron with which it is revolving is $\quad \times 10^6 \mathrm{~ms}^{-1}$. Given mass of electron $=9 \times 10^{-31} \mathrm{~kg}$.