Question

A proton traveling due north 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 proton continues to travel in a straight line due north. In which direction must the magnetic field lines point

Answer 1

The proton must be experiencing a magnetic force to the east that counters the electric force pushing west, allowing it to continue north. The right-hand rule determines that the magnetic field must be directed downward to cause this eastward force.

Step-by-step explanation:

Since the proton is continuing to travel due north without deviation and it is known that the electric field points due west, we can infer that the magnetic force is balancing out the electric force. The proton, having a positive charge, would naturally be pushed in the direction opposite to the electric field, which would be due east. However, since this is not occurring, the magnetic field must be exerting a force in the eastward direction that counters the electric force and keeps the proton moving straight north.

To determine the direction of the magnetic field that would result in such a force, we can apply the right-hand rule for the force on a moving charge in a magnetic field. The thumb of your right hand represents the direction of the proton's charge (moving north), point your fingers in the direction of the desired force due to the magnetic field (east), and then extend your middle finger perpendicular to your palm. Your middle finger will now point in the direction of the magnetic field, which in this scenario would be directly downward. Consequently, the magnetic field lines must be pointing downward to achieve the observed motion of the proton.

This example illustrates the principle that magnetic fields exert forces on moving charges, and these forces are perpendicular to both the velocity of the charge and the direction of the magnetic field as dictated by the right-hand rule.

Answer 2

upward

Step-by-step explanation:

In the electromagnetic system of force if the direction of motion of proton does not changes it means that the electric and magnetic forces are such a ways that they are cancelling each other's effect.

Since, electric field lines will exert a force on the proton to the west, hence, the magnetic force must force it to the east. It is well known that magnetic force acts perpendicular to the direction of magnetic field. magnetic field should point upward direction.