A proton is moving undeflected in a region of crossed electric and magnetic fields at a constant speed of \( 2 \times 10^{5} \, \text{m s}^{-1} \). When the electric field is switched off, the proton moves along a circular path of radius \( 2 \, \text{cm} \). The magnitude of electric field is \( x \times 10^{4} \, \text{N/C} \). The value of \( x \) is __________. Take the mass of the proton \( = 1.6 \times 10^{-27} \, \text{kg} \).
