Answer:
The direction of the magnetic field is in the z-direction
Explanation:
Applying right hand rule, which states that when the thumb, index finger and the middle finger are held mutually at right angle to each other, with the index finger pointing in the direction of the moving charge (y- direction), the thumb pointing in the direction of the magnetic force (x-direction) pushing on the moving charge and then the middle finger pointing in the direction of the magnetic field (z-direction).
z direction.
Using John Ambrose Fleming's right hand rule which asks to position the middle finger, the thumb and the index finger as follows;
| thumb
|
|
index |
/
/
/
/
middle
With this arrangement shown above, if you point your index finger in the direction in which the charge is moving, and then the middle finger in the direction of the magnetic field, then your thumb will point in the direction of the magnetic force.
For example;
If a charge is moving in the x direction, and the magnetic force is moving in the y direction, then the above figure is rotated to make sure that the index finger is pointing in the direction of the moving charge so as to get the direction of the magnetic field as follows;
y| thumb (magnetic force)
|
(direction of charge) |
index x |
/
/
/
/ z
middle (direction of field)
Therefore, the magnetic field is in the z direction.
Now to the question, if the charge(electron) is moving in the y direction at right angles to a magnetic field and it experiences a magnetic field in the x direction, the diagram above can be rotated to depict this situation as follows;
y| index (direction of charge)
|
|
| x
/ thumb (direction of force)
/
/
/ z
middle (direction of field)
Therefore the magnetic field will move in the z direction.
Note:
i. For every rotation of right-hand, the index finger must always point in the direction of the charge.
ii. Since the question does not specify which direction the electron is moving in (whether positive or negative), the direction of the magnetic field (whether positive or negative) might not be determined either. But in either case, the field will move in the z direction.
