Question

An electron traveling due south enters a region that contains both a magnetic field and an electric field. The electric field lines point due west. It is observed that the electron continues to travel in a straight line due south. In which direction must the magnetic field lines point?

Answer 1

The direction of the magnetic field lines should point into the plane (downwards).

Step-by-step explanation:

Direction of motion of electron v = south.

Direction of electric field E = west

As the electron is negatively charged

Direction of electric force = east

Now:

we know that magnetic force = q * V X B

for force to be in west direction

The magnetic field lines should point into the plane (downwards).