A particle of charge $- 16 × 10^{-18} C$ moving with velocity $10 ms^{-1}$ along the x-axis enters a region where a magnetic field of induction B is along the y-axis and an electric field of magnitude $10^4\, Vm^{-1}$ is along the negative z-axis. If the charged particle continues moving along the x-axis, the magnitude of B is

$10^3 Wb/m^2$

Since Charge continue to move along x axis. Net force = 0

$\Rightarrow qE = qVB$

$\Rightarrow E = VB$

$\Rightarrow B = \frac{E}{V}= 10^3 Wb/m^2$