An electron enters a crossed electrical and magnetic field region with a speed of $100 m s^{-1}$ along +x-axis and passes undeviated. The strength of magnetic field is 5.0 T and it acts along +z-axis. Give the electrical field in vector notations indicating its magnitude as well as direction:

$\left(500 Vm^{-1}\right) \hat{j}$

The correct answer is Option (1) → $\left(500 Vm^{-1}\right) \hat{j}$

for electron to remain undeviated,

$F_e=F_B$

$qE=q(V×B)$ [$q(V×B)$: Lorentz force]

$E=V×B$

$=(100\hat i)×(0.5)\hat k$

$=500\hat jV/m$