Question

An electron in a uniform electric and magnetic field has a velocity of 1.20  104 m/s (in the positive x direction) and an acceleration of 2.00  1012 m/s2 (in the positive z direction). If the electric field has a magnitude of 20.0 N/C (in the positive z direction), what can you determine about the magnetic field in the region? What can you not determine

Answer 1

1)

$$B_z=0\\F=ma=-eE-evB_y\\ 2\cdot10^{12}=-20(1.759\cdot10^{11})\\-(1.759\cdot10^{11})(1.2\cdot10^{4})B_y\\B_y=-2.61\cdot10^{-3}T$$

2) We cannot determine x-component of magnetic field.